Photoelectric effect

Grecia S. Laboy

The photoelectric effect is the emission of electrons from a metal when you affect it electromagnetic radiation (visible light or ultraviolet light, in general). Sometimes the term is included in other types of interaction between light and matter. The photoelectric effect was discovered and described by Heinrich Hertz in 1887, noting that the arc jumps between two electrodes connected to high voltage reaches greater distances when illuminated with ultraviolet light when left in the dark. The theoretical explanation was made by Albert Einstein, who in 1905 published the groundbreaking article "Heuristics for the generation and conversion of light", basing his formulation of the photoelectric work on an extension of the Max Planck quanta. Robert Andrews Millikan later spent ten years experimenting to prove Einstein's theory was wrong, to finally conclude that if the Photoelectric Effect era. The derive the equation that describes this effect in order to calculate Planck's constant and determine the work done to remove these electrons from the material. It was therefore necessary to turn on the mercury lamp and choose the lines of greater intensity. Thus, we analyze how much voltage was needed to remove electrons in different rays of light. Thus, we find the relation proposed by Einstein to explain the photoelectric effect (electron kinetic energy gives a straight line by changing the frequency of light). The slope of this is needed to calculate Planck's constant by several equations, because this is equal to the ratio of the electron charge, h (m = h / e). The product of the potential work load is (by definition of potential V = W / e). Assuming the value of the intercept will tell us the amount of work necessary to remove these electrons from the material provided. This tells us that the intercept of the equation it means is the potential to cut or braking. This cutting potential is independent of radiation intensity (I), but depends on its frequency. To derive the equation describing the photoelectric effect which is E_K=ν*h-W where the frequency of light radiation, h is Planck's constant and W is the work required to move an electron energy level. E_K is the kinetic energy of a photon emitted. We modify this equation dividing by the base load "and" and obtained a new equation: V=h/e ν-W/e

For each color there is a radiation frequency of light and a single voltage. During this experiment we measure the voltage with the team badge of each color and then create a graph of voltage vs. frequency. We relate the value of the slope of the graph with the slope of the equation "m = h / e" and cleared in order to find "h" Planck's constant experimental. Plank's constant is used to relate dimensions of mass or energy with dimensions of length or time. Because the focus of the experiment units are Planck's constant joules * seconds (Js). Using this graph and the equation above also relate the intercept value of the intercept found in the equation "b = W / e", the clear stand "W", work in units of joules (J).

The Visible Spectrum… not exactly for everyone 

Juan E. Miranda Sanfeliz

In our Physics II course, we have studied many topics that go from electric current, magnetic fields, circuits, light, etc. Two topics that caught my attention were the visible light and the human eye. As to why I was attracted to them was, the beauty that is our eyes for the way they produce images for us, and the light for giving us those unique colors for each of those images.  In our course book, we can find information of two common defects of the human eye like myopia (nearsightedness) and hyperopia(farsightedness). Sure, these are very common amongst us and that’s why a lot people wear glasses of eye contacts, but the defect that I was curious is one not so common… colorblindness. 

For better understanding of this eye defect, is best if we remember how our eyes work. The human eye sees by light stimulating the retina. The retina is consists of a complex array of nerves and receptors that are called rods and cones. The rods give us our night vision, but can’t distinguish color. On the contrary, the cones perceive color during daylight conditions. These cones contain a light sensitive pigment sensible to wavelength that goes from 400nm to 750nm, also known as the visible spectrum.

Color deficiencies as many call it, can be associated with aging but nearly all color deficiency is hereditary. The most common form of color vision, the red-green deficiencies, has been proven to be due to sex linked X- chromosomes and simple recessive hereditary traits. What’s really interesting about this condition is that a color defective male always inherits his deficiency from his mother, even if she doesn’t have color blindness; she only is the carrier of the defect. The mother would receive the color deficiency gene from her father, only if he was colorblind, or from her mother that could be a carrier o colorblind, although that last one is very improbable.  

The rareness of this disease, if you call it that way, is the many types of colorblindness that they are. Many people think that if you’re colorblind you see everything around you black and white, like there was only one type of colorblindness. Fortunately for me, I knew to make this distinction because I had a History in middle school that was colorblind but his problem was with distinguishing between blue and yellow. One time, he was making a painting of a fairy with a blue dress for her niece and he ended up painting it green. Remembering that, I looked up different types of color blindness, or color vision deficiencies if you will. Base on clinical appearance, color blindness is described as total or partial.  Total color blindness is much less common that partial color blindness. Under the partial color blindness, there are those who have trouble distinguishing between and green and those who have trouble distinguishing between blue and yellow. The most common defects of the last ones mentioned are protanopia (absence of red retinal receptors), deuteranopia(absence of green retinal receptors, and tritanopia (absence of blue retinal receptors). An example of these deficiencies is given in the next picture: 

I know it may be sound a little awkward me seeing this, but I think is something really amazing. In our world, many things are distinguish by their color, like the grass, the clouds, the sky, to name a few, and to know that people out there haven’t seen difference. One time I was in the US for a vacation, and we stop at a red light. When I noticed, the red light had like a blinking white like in the form of a tube in front of the red bulb. I remember that I asked what was that and my cousin who lived there at the time told me that that was for the colorblind, especially the ones suffering from protanopia. After that I wondered if there was some kind of treatment for this so that people didn’t to depend on “the blinking light”. 

 

And so, like myopia and hyperopia, you can use lenses to adjust your color sensation because you can’t really improve color vision.  This concept of using lenses for correcting color vision deficiency dates back to the 1837 when a German scientist named Seeberg wrote about the possibility of correcting color vision deficiency using some sorts of lenses. But it wasn’t until the 20th century that different types of tinted lenses were developed to help colorblind improve their vision. As I mentioned before, these lenses can’t correct your color deficiency, just enhance your color perception. But like all things, it has its cons. Studies have found that color perception improves your problem area like red-green but at the expense of an increase in blue-green confusion, and that you might experience impaired judgment of distance and motion. Another con for these lenses is the cost, like $500 per lens, so not many people would be willing to pay such a high price for something that isn’t exactly a real solution for the problem, unlike a diverging lens that corrects myopia. 

Reading about all this, is obvious that I learned from this “rare disease” (around 5% to 8% of the world population is colorblind) like that it is a hereditary disease, that there isn’t a cure or remedy per se for it and why people with it choose just to go on with their lives like there’s nothing wrong, maybe just confusing one color with another.  But what I’m really interested is in meeting someone with total colorblindness and ask him questions like, “how your color vision deficiency has affected your performance at work?” and many others. If I had not read that part of the visible spectrum and of the human eye in our course book, I don’t think I would have read about this topic and want to look for my History teacher to maybe talk to him about something in his life other than his class.  And so, I think the Physics II course achieved its goal.  

References: 

• Giancoli, Douglas C. Physics for Scientists & Engineers with Modern Physics. 4th ed. Vol 1. Upper saddle River, N.J. Prentice Hall, 2009. Print.

• http://colorvisiontesting.com/color2.htm

• http://www.colblindor.com/2008/03/29/improving-color-vision-with-lenses-for-the-colorblind/

• http://www.colour-blindness.com/solutions/cure/

Electromagnetism – Distressed Core

Gladys N. Vega Vigo

Sound waves and electromagnetism

If we know that sound gains wavelength and looses frequency as it travels through more dense materials, then the anomalies in these waves are the means by which we can surmise the fundamental architecture of our planet. The behavior of our planet, including fauna and flora, nature itself, can be explained by the effects of electromagnetic waves.  Parting from this, let’s assume the following: if a lot of people die at the same time, at the same place, let’s say, at a perimeter of two miles, and a nerve agent is not the cause of their deaths, there’s no variation in sex and age, but they all have pacemakers; then they are all susceptible to electromagnetic interference (electromagnetic impulses).

Birds navigate by sight in a short range but in a long range by magnetic fields.  Little ions in their brains and vision system help them navigate using the magnetic field.  Following this same line of thought, if we have a flock of birds flying violently and uncontrollably (frenzy swarm of birds) and we know it was not deliberately and it is reported, say, 53 times in different parts of the planets, then their navigation system might have been affected by electromagnetic waves.

What would be the cause of a distressed core?

Wrapped around the Earth is an invisible field of energy made of electricity and magnetisms, reason for what it’s called the electromagnetic field (EM field).  It is where we get our electromagnetic North Pole and South Pole. This field protects us from magnetic radiation, but recently it’s been slowly falling apart. The Earth is composed of the crust, mantel, and the core – inner and outer core. The inner core is a big chunk of iron. The outer layer is made of hot iron and nickel at 900 degrees Fahrenheit (2,000 miles down and 1,000 miles thick) which is constantly spinning in one direction, which makes the electromagnetic field. The core is the engine that drives the electromagnetic field.  And that’s where we get our problem, this engine has begun to stall; the core of the Earth has been slowly stopped spinning. The problem:  it cannot be stopped.  As the EM field becomes more unstable, we would begin to see isolated incidents. If it were the case that we observed this phenomenon in our present day, in a few months everything electronic would be fried. The static charges in the atmosphere will create super storms, with hundreds of lightings strikes per square mile. The Earth EM field shields us from the solar winds, which are a lethal blend of radioactive particles and microwaves. When that shield collapses, the microwave radiation will find a way to escape and literally cook our planet.

The deepest we’ve been to the core is 7 miles with a two inch drill-bit. We’re talking about millions of pounds per square inch of hot melted metal.  Even if we come with a brilliant plan to fix the core we just can’t get there. On the other hand, if we somehow find a way to get to the core, the only way to fix it to its natural rotation would be with a massive explosion. We have to use wave interference in order to reestablish the rotational force of the core, because one explosion just won’t do it. Is like stones in a pond. A big stone thrown into the pond will only do a big splash. But with smaller stones, we wait until the wave is weakened and we throw another, and another and another. The ripples reinforces into geometric progression. We hold bigger than assemble apart and we’ll have hundreds megatons explosions instead of one big bang. Hence, we would see them through the core and we would haste them accurately to the inch, we detonate them in a sequence that has to be accurate to the millisecond and we would outrun the biggest nuclear shockwave in history.  If there was a problem with this plan of action, it would be that the last bomb won’t be enough and it has to be at least 30% larger in order to maintain the rotational force; meaning it will need several dozen more pound of plutonium.

In these examples it can be observe how important the electromagnetism/electromagnetic field is in our everyday life and the proper functioning of our planet.  Life isn’t simply a gift or a means of consuming, to some, our planet’s endless natural resources. Rather is a means of perfectly balanced cycles that have kept our planet alive for so many millions of years. Let’s hope that our future generation can realize the importance of this perfectly assembled balance before anything worse happens.

Renewable Energy

Daniel Maldonado Sanchez

In our days, Puerto Rico is passing through a lot of economic problems, for example, no money for education, food or to pay the basic living things like the services of water and electricity that every day become more needed with all the technology thats coming out. We know that the resources that we use today are more expensive than ever. One of the most necessary resource for us is the electricity. As the usage of this resource becomes higher the cost also becomes higher because more oil is needed to produce it and the oil is a really expensive fuel. This resource is very important because we use it every day to study, work, eat, travel, etc. A lot of people have or have had problems with the cost of the electricity and many of them don’t have enough money to pay the high price of it. Some of the people that really don’t have the manner to find the money to support these high prices tend to steal it. However is important to know that the method of stealing it is obviously not the best and that there are many others alternatives that could be made to have this important resource without steeling it.

The renewable energy is energy that comes from natural resources that involves the use of sunlight, wind, rain and water. If we talk about the sunlight we can refer as photovoltaics. Photovoltaics is the direct conversion of light into electricity at the atomic level. The photoelectric effect that some material exhibit cause the absorb photons of light and release electrons. This occurs in the solar cells that are made of semiconductors materials such as silicon. When light strikes the cells, a portion is absorb and transfer to the semiconductor, the energy knocks electrons loose, allowing them to flow freely. When these electrons are captures, an electric current results and can be used as electricity. This solar cells can be connected in both series and parallel electrical arrangement to produce any required voltage and current combination. This use is one of the best solutions because the sun's rays give off approximately 1,000 watts of energy per square meter of the planets surface. If we collect all of that energy we could easily power our homes and offices for free.

Other renewable energy is the wind, we can use the term eolic energy. The wind energy is the energy generated by the wind and can be used directly or be transformed as electric power. It consist to use windmills for mechanical power. This method uses the kinetic energy generated by the effect of the wind. Wind energy is currently the fastest growing renewable energy and represents a large portion of the electric production.

Every time a drop of water from the rain impacts on a surface it is an opportunity missed. Each raindrop has an impact energy that is highly dependent on the size of the drop; from a small drizzle drop that has 2 microjoules on impact, to a downpour size drop that carries 1 millijoule of impact energy. A team of scientist identified that a piezoelectric material might be able to capture that energy. Piezoelectric materials generate an electrical potential when acted on by an outside physical force in this case a raindrop. They were able to capture between 1 nanojoule and 25 microjoules of energy per drop. The total power will vary incredibly depending on the conditions, but the device produces about one microwatt of power in a light drizzle. This type of device might work quite well for sensors, especially if the sensor is detecting rain. For example a weather sensor that would only send a signal of how hard it is raining, when it is in fact raining. Or how about sensors that will automatically close your house windows when a storm suddenly appears. This technology will not make up a large portion of our energy, but capturing the available energy all around us is certainly a good idea.

Another important type of renewable-energy is the water energy. Flowing water creates energy that can be captured and turned into electricity. This is called hydroelectric power or hydropower. The most common type of hydroelectric power plant uses a dam on a river to store water in a reservoir. Water released from the reservoir flows through a turbine, spinning it, which in turn activates a generator to produce electricity. But hydroelectric power doesn't necessarily require a large dam. Some hydroelectric power plants just use a small canal to channel the river water through a turbine. Another type of hydroelectric power plant, called a pumped storage plant, can even store power. The power is sent from a power grid into the electric generators. The generators then spin the turbines backward, which causes the turbines to pump water from a river or lower reservoir to an upper reservoir, where the power is stored. To use the power, the water is released from the upper reservoir back down into the river or lower reservoir. This spins the turbines forward, activating the generators to produce electricity. A small or micro-hydroelectric power system can produce enough electricity for a home, farm, or ranch.

As we can see through out all the information found the renewable energy is a method that every place of the world should be using because its very environment friendly and would contribute to a more safe and pure way of living. The use of crude oil to generate electricity is one of the main causes of Global Warming and as we said earlier renewable-energy is a very resulting way to safe the Planet. There are more ways of this type of energy but the ones that we mentioned here are the most commonly used. We have to choose if we continued to use non-renewable energy or start using renewable energy.

Reference:

Callihan, Jean. 2010. Hydropower. Taken http://www.renewableenergyworld.com/rea/tech/hydropower the day 29 of november 2011.

Company Sun & Climate. Taken from http://www.sunandclimate.com/products/6-wind-energy.html the date 27 of november 2011.

McGee, Tim. 2008. Renewable Energy. Taken from , the http://www.treehugger.com/renewable-energy/the-power-of-rain-alternative-energy.html, the date 28 of november 2011.

Types of Renewable energy. Taken from http://www.renewableenergyworld.com/rea/tech/home the date 29 of november 2011.

Jumping movement: art in psychics 

Eduardo A. González Falcón

Jumping or the motion of lifting a mechanical system through the air along a ballistic trajectory is a body movement that has also intrigued me. For decades I had been jumping in different sports and have always wondered why it is so versatile. Our bodies are the mechanical system as described by the meaning and we move along a trajectory just as a projectile, so there are all kinds of jumping forms which result in different distances. In volleyball and basketball some jumping movements are completely vertical, which are called vertical leap and they are created by the human body as a upward force in a same line with different height above the ground. Just as most power and mechanic systems, jumping requires great power and force in order to surpass the bodies’ gravitational force to the ground. Many people have asked me why I can jump higher than most with less difficulty, its simple the greater the speed and force the greater the power. So a skinny 150 pound body that has the same leg strength as a 200 pound body would be more likely to jump higher due to its less weight force on the ground. The other aspect which most people don’t see when jumping is the speed in which you create the force. Like in most extreme sports, the greater the velocity of a skateboard or motorbike the more distance they are going to travel and more “airtime” they are going get. Those kinetic basics are the same in the human body; the clear reason why long jump athletes start their jump approach by running a short distance with great velocity. 

I visualize jumping as watching spring, the greater velocity and force done the more “pop” it is going to have and the higher and longer it will go. To find the force of a spring we calculate F=Kx where K is a constant and x is the distant vector. The same in the human body, the force to jump upward is determined by the k, which is the force constant depending on the material it is composed by (in human body visualize less mass as more powerful material due to explanation of less weight carried by object) and it also depends on the x which is the distance it can stretch. That is the reason why high jump athletes and ballerinas jump so high with so much flexibility; their muscles are normally larger, thinner and can stretch easier. It is scientifically proved that a person jumps higher when their muscles are warm and stretched because their reaction time when their bodies undergo a change in the downward/upward motion is less. Also they will more potential energy stored having greater velocity and force in that moment. 

Another great questioning the basketball dunking world is the theory behind vertical leap time or as they call it “hangtime”. Why athletes like the great Michael Jordan appear to fly when they jump. All objects, in this case people have the same gravitational acceleration when they are falling to the ground which is 9.81 meters per seconds square, so appearing to have greater projectile airtime is a question of vertical displacement in the x direction with an initial jumping angle involved. A basketball superstar that has a 50 inch vertical can be less time in the air than Jordan by the only reason of the initial distance it takes off. Running then jumping from a far distance like 15 ft at a 45 degree angle will cause greater air time than elevating from a standstill position. For me the jumping movement is a great locomotive motion which I see it as an art form that involves different physics and biomechanics explanation. The ability and creative way the human uses different jumping forms is why it gives It such a versatile form of motion which it is expressed with emotions and requires great talent. Extreme sports have greatly benefited in the creation of innovative materials in their respective mechanical systems, for example skateboards which were invented no more than a century ago, have evolved greatly and the continuous research for more environmental and productive wood material will continue to go on so  the human raises the bar higher and higher each time. 

Photoelectric effect

Marangelí Acevedo Castro

Recently in physics class we discussed the photoelectric effect developed by Albert Einstein. This photoelectric effect consists of a metal with one valence electron which is released when a photon has the enough energy to release it when is irradiated by an electromagnetic radiation, which usually is UV light. Then all valence electrons emitted by all the atoms of the metal are used as current. The photoelectric effect has a lot of uses like sensors, spectroscopy and solar cells among others.

I asked myself what if instead of using a metal with one electron in its valence shell, use a metal with two valence electrons? Or what if we can irradiate more UV light to a solar cell and not only the one emitted by the sun? Probably it would be more difficult for the electrons to be released because they will have more attraction or force between them making it more difficult to be released by the atom. If this was possible, assuming there is no attraction between the two valence electrons, a solar cell could generate, in theory, double the current a normal cell would with a metal with only one valence electron. The photons causing the release of the valence electron will need to generate more energy in order to excite the electrons and produce the current. I believe that the UV light emitted by the sun will not be sufficient to generate the amount of energy needed for the electron release. This is why I asked myself the second question mentioned before. 

I read that if the light intensity is increased, this will increase the number of the photons and therefor it will be easier to release more valence electrons from the metal in the cell. After knowing this I wondered if maybe increasing the light intensity we could release the two valence electrons in the metal. In the course of physics we also learned that when a mirror is irradiated by an incident ray it is reflected with the same angle of incidence but it takes another direction unless the angle is perpendicular to the surface of the mirror. This law of reflection varies depending if the surface of the mirror is flat or with a curvature. Knowing this I thought that placing specific mirrors around the solar cell could be useful to generate more light intensity for the electron emission. Examples of metals with two electrons in the valence shield are zinc, copper, nickel and iron, among others. In my opinion I think a solar cell that could generate more current will be great for the electricity used in a house; saving energy, money and helping the environment. 

Why not use renewable energy?

Valerie López Carrasquillo

Energy availability of renewable energy sources is higher than traditional energy sources, yet their use is limited for now. In the following model of sustainable energy development, renewable energy sources are considered inexhaustible (sort of unlimited) while also having the advantage of clean energy (no pollutants are made during the process), defined by the following features:

-The energy-conversion systems pose a low-to-none environmental impact.

- No added potential risks in their use.

- Indirectly enrich other natural limited resources

- The proximity and transportation of energy to production sites to consumption sites may be easier in many cases.

- It can be an alternative to conventional energy sources, with the high possibility of starting a process of gradually replacing them.

Using renewable energy we could do many things; Many people like to exercise in the house and do not connect circuits to transfer that energy to household utensils such as stove, refrigerator, TV, etc..

Even better why not create a kind of fan that is loaded with wind and then use that energy to make the fan as you marched for renewable energy in the home electronic devices.

I found this on the internet that is a small example of how we could use renewable energy:

The energy must be generated, stored, processed and transported to be consumed by people, factories and other types of energy-consuming artifacts. Depending on various factors, like the distance between production and consumption centers, the economic and environmental costs are affected.

From a bigger point of view, the production and consumption of energy is, most likely, the biggest and most important instrument for development and production of practically everything, and it is directly linked to welfare and economic growth, which means that an increase in clean energy offer could allow companies to increase their demand without environmental impacts while also increasing their production facilities and growing as a company too.

Modern societies also wish to have a healthier environment, so they’re also trying to minimize any ecological impact involved in the energy production from traditional sources such as Natural Gas and Oil. It is for this important reason that the most important factor today is to encourage energy-saving methods while also introducing cleaner energy production facilities to minimize any kind of negative impact while also improving energy efficiency in consumer products, industrial process, transportation and others.

Today, modern companies have also made the jump into cleaner energies by themselves, and have even found ways to use energy with the use of cogeneration systems, as in, systems that allow the energy released to be reused, and in doing so avoids spending more on production. An example of this is the regenerating braking system found in hybrid vehicles: When the driver brakes, the driveshaft is separated from the wheels and starts to rotate an electrical alternator that, while braking the car, recharges a battery and recovers some of the energy used to push the car in the first place. Also, institutional and government campaigns have started to offer different incentives to promote the use and installation of renewable energy systems in houses and manufacturing facilities throughout the country. Industrialized countries, in order to avoid energy dependence to third parties, are encouraging diversification of energy sources and trying to achieve the most energy-auto-efficiency possible with renewable energy sources and minimizing the use of traditional not-renewable ones.

With all this, is done to minimize the environmental costs, maintaining the same levels of "being made" in part by reducing pollution, and complies with international agreements to preserve the environment.

Nevertheless, they still do not solve the major outstanding issues of resource depletion, and the total suppression of acts that cause environmental problems. Just as obvious is the solution to address an inequality different energy between countries.

Static electricity shock in your home

Kevin J Bergollo Lorenzo

When the cool and dry weather is around almost everything you touch made you feel an electric shock. This effects are very common for those how live in near to the north were the temperature are low then 50oC. Static electricity is refers to the buildup of electric charge on the surface of object, when electrons move from one surface to another through contact. All material is made of electrical charges in the material atoms. In the universe there are equal amount of positive charge and negative charge, these particles always try to stay in balance by Coulomb’s law F=(Q_1 Q_2)/(4πr^2 ε_0 ), forcing the same amount of particles to move from one side to another. When one object is in contact with another object some of the charges redistribute from one material to the other. The electric field is created when charges are moved by a force, E=F/q. If one of the charge materials touches a conductor, like a metal, the charge will neutralize itself, living positive charge on one object and the same amount in negative charge on the other, Gauss' law states that "the total electric flux through a closed surface is proportional to the total electric charge enclosed within the surface", so the potential difference is ΔV=∮_s^ ▒〖E*dA〗. 

So, why you feel a static shock when you made contact with some metal, like the doorknob? Well, most of the people have insulator in their homes and in them self, like the rubber soles of a shoes or a wool carpet in the floor. When you walk on that wool carpet, your body builds up a charge it can’t get rid of because the insulator of the shoes. The air when it dry work like insulator, that why static electricity are more common in dry winter months, that so when you touch that metal doorknob feels el shock in it. Walking around is not the only way to generate electric static, some time sitting in a chair and creating contact between your clothes and the chair can generate a lot of static on your clothes. While the body stays on contact with the chair your body voltage stays low, if the body is separated from the chair, take the charge with it, rising up your body voltage. Not all people feel the same way with the same amount of charge in the body. Some people are more sensitive to shocks than others, for some people the range for feeling the electricity is 2.00V – 4.00V. In other cases some bodies store more static electricity, all depends on the size of the bodies, the size on the feet and the thickness of the shoe soles. Some of the remedies to lower the electrostatic in your home are raising the air humidity to a 40-50% with a humidifier. Also is prefer to use leather soles shoes, there are some antistatic sprays available to treat chair and other furniture. The spark can provoke fire or even worst can be extremely dangerous in combination of a combustion gas.

Measuring the speed of light with a microwave oven

Moisés Montalvo Lafontaine

To measure the speed of an object we just need to know the time it takes the object to travel certain distance and use Newton’s law of motion. It sound simple and it is. But how the speed of light is measure using this technique? Well is hard to do it with accuracy because the speed of light is so high that the time it takes to travel some measurable distance is extremely small. So I wonder how it was measure. But most important to me is how I can measure it myself. Well it turns out to be easy to do and we all have the equipment to do it: the microwave oven.

First let’s explain the early attempts to measure the speed of light. Galileo tried to measure it using a lamp at a great distance but he concluded that the speed must be extremely high to be measure. To perform better measurements it was required a laboratory environment. Albert A. Michelson used the rotating mirror apparatus shown below. This had higher precision than previous ones and it gave Michelson a good value of the speed of light in the air. As we can see in the diagram the apparatus measurement was purely mechanical. But with this apparatus Albert A. Michelson performed measurements good to nearly one part in ten thousand. 

(http://www.setterfield.org/assets/images/cx4_clip_image001.gif)

With the advances in technology, better measures were made at the National Institute of Standards and Technology (NIST). This new techniques reduced 100-times the uncertainty for the value of the speed of light. Of course is not a technique as simple and mechanical as the early ones because it’s based in the atomic/molecular measurements using a helium-neon laser. The speed of light is defined to be 299,792,458 m/s (or 3 X 10^8 m/s when high precision is not require). Because this value is constant the meter was redefine in terms of the speed of light using the relation c=νλ. 

Like a mention before, we can calculate the speed of light using a microwave oven. We can do it theoretically or experimentally. The frequency v in a microwave oven is usually 2.45 gigahertz. At this frequency, water molecules resonates releasing heat. The distance from peak to peak of microwaves (wavelength λ) is almost 12.2 centimeters. So using the formula c=νλ we obtain c=(2.45X10^9 Hertz)*(0.122 m) = 2.989X10^8 m/s. This result was obtained using the theoretical values of the microwave oven operating frequency and wavelength. How can we determine this experimentally? First, and very important, we have to take out the rotating plate. What this plate does is rotate the food so it can be heat evenly because the microwaves are emitted “linearly”. Use cheese and microwave it for a couple of seconds. The cheese is going to melt but not uniformly. Is going to melt only in the spot were the microwave hits it. Measure the distance (in meters) between the centers of the spots. That distance is half the wavelength of the light so it has to be doubled in order to obtain λ = 0.122 m. Multiply that by the frequency of the microwave v = 2.45X10^9 Hertz and the velocity of light (in the air) is obtain.

http://www.scientificamerican.com/article.cfm?id=microwaves-and-the-speed

http://www.scientificamerican.com/article.cfm?id=how-the-microwave-works

http://www.scientificamerican.com/slideshow.cfm?id=how-the-microwave-works

Interference and diffraction throughout physics

Luis A. Muñoz Torres

The sources are those that emit coherent light waves of the same wavelength or frequency which are always in phase with each other or have a constant phase difference. The two coherent sources can produce the phenomenon of interference. The colors that we see when sunlight falls on a soap bubble, a little oil or wet pavement, or a red hummingbird are caused by interference of light waves reflected from the front to the back of the surfaces of thin transparent films. This is because two beams of waves arriving at the same level if they add their effects in phase or counteract its effects if they date. Their combined effect is obtained by adding algebraically the displacements at the point to the sources individually. This is known as the principle of superposition.

Young's experiment seeking behavior or the nature of light. With a dual-slot grille experimentation was carried out very similar to this interference experiment which sought to show whether light consists of particles or waves passing through the dual grid. Was observed pattern formed on the white screen. If light consisted of particles have been observed two white stripes on the screen however, there was a distinct pattern on the screen which had a larger line in the center and smaller stripes on each side. This is due to the phenomenon of wave diffraction and interference the light passing through the diffraction gratings and then suffer the light of the grids interferes with light passing through the other grid and that is why it forms a most intense line in the center of the screen. There is constructive interference and destructive interference that is why we see dark spaces between each line and in the center look brighter light because there we have constructive interference.

Data obtained in the experiment shows the distance between the center of the peak and each peak. The light intensity as a function of linear position. The peaks represent locations where the bands are intense in the white screen (constructive interference) and represent the minimum destructive interference. As the number n peak distance increases and the peaks are decreasing intensity. The formula that relates the distance (Dx), the wavelength (λ), the separation between the slits (d) and the distance between the device and the sensor grid of light (L) is: dΔx / L = nλ.

We show the behavior of interference of light waves. It can be seen clearly as peaks and troughs are not defined very well. This is why the measure was taken away from the low near each side of the central peak. Constructive and destructive interference cannot be seen as clearly as when using the dual grid.

By observing the behavior of light diffracted as it passes through the interference grids shows that the laser passes through the grid divided into upper and lower those in the light sensor as points. This is because the light as it passes through the grating is diffracted simple. In the experiment of additional double grating diffraction, we observe the interference effect in which the peaks of the wave are altered as two waves intersect and cause interference.

Omar R Diaz Rodriguez: The Physical Formulation behind the Refrigerator

After looking at the device closely, one is able to observe the physical formulation behind it. A refrigerator is a common household appliance that consists of a thermally insulated compartment and a heat pump  that transfers heat from the inside of the fridge to its external environment so that the inside of the fridge is cooled to a temperature below the ambient temperature of the room. The purpose of the refrigerator is to keep whatever is put inside it cold. This device use an ingenious system to move hit from inside out by transferring heat. To create cold a fridge absorbs hot air and dumps it outside, furthermore for that it relays in a system of coils. 

With this object, an aluminum coil inside the refrigeration chamber forms the evaporator. The cooper coil that snakes around the outside of the chamber, under the fridges metallic shell, is the condenser. Nevertheless, both sets of coils are responsible for the heat transfer. They move the heat from inside the fridge to the outside air, leaving cold air behind in the chamber.

For this purpose, once the heat is absorbed by the coils, the cold air left behind needs to be preserved; hence insulation surrounds the fridge chamber. To this end, every space and every crack is field from the air tight sealed of rubber stripping around the door to the polystyrene and insulating foam in its walls. As a result, the insulation keeps the cold air in, and the heat out. Furthermore, that includes the heat that is expelled by the fridge itself.  

On the other hand, the evaporator coil is nestled between the fridge and the freezer. The coils are filled with refrigerant, a special mixture of chemicals called hydro floral carbons, which have the unique property of easily absorbing and releasing heat. Additionally, in order to achieve refrigeration the evaporator coil is strategically placed, since hot air rises it comes into contact with the evaporator coil that sucks up the heat leaving cold air behind. The condenser coil wraps around the extremities of the fridge getting rid of all the heat and expelling it into the cooler air around the fridge. 

With this object, to fully understand the physical formulation behind the product it had to be dissected. With the use of a screw driver the door was extracted, in addition the shelves and the outside layer of the refrigerator were taken out in order to analyzed the inside of the device. It is important to mention that to carry out this procedure, one must use safety equipment.

In addition, is important to specify that the refrigerator that is being analyzed is a cabinet-depth refrigerator. With this purpose, the consumer has some pros and some cons when buying this type of refrigerator. Some advantages of buying this model are that this one sticks out only a bit farther than built-in models and that usually accept extra-panels for to achieve a custom look. On the other hand, some disadvantages are that this model has less space than the deeper freestanding models and cost more.

Gravitation and dark energy

Francisco J vergara 

If we look back at our principles of gravity it will be clear that objects tend to attract each other’s. If we apply that to the universe, knowing that the universe is full of matter the attractive force between matters will pull all matter together. If we know this we could say that in theory the expansion of the universe had to slow, to a point that it would stop and recollapse.  But certainly that’s not happening. In fact recent studies prove that the universe has been accelerating. But what is causing the universe to accelerate it expansion? Maybe there is something wrong with the Einstein theory of gravity? We really don’t know but Theorists gives the solution a name ‘Dark energy’

But what is Dark energy after I make my research in this topic I realize that there is more unknown than know, the only know is that it’s affecting the universe expansion. In fact we could say that practically nothing is known and that’s what makes this topic so interesting. There are some theories about dark energy first we have Einstein theory that says that empty space can possess its own energy and  as more universe come into existence there would be more energy and so on this continuous expansion and acquirement of energy will cause the universe to accelerate faster and faster but this is only a theory.

Another theory that I found pretty interesting is that dark energy could be a new form of energy fluid or field. But this is no normal energy at least not as we know it, this kind of new energy will have an effect on the universe expansion that is totally the opposite of that of normal matter and energy. If it it’s totally opposite that could perfectly explains why universe is accelerating. Matter and normal energy will cause the universe expansion to slow down but this kind of unknown energy will cause it to accelerate. If we take a look at the numbers we could see that there’s only 5% of normal matter in the universe 75% of dark energy and 25% of dark matter. Then it is obvious that there is more energy making the universe to expand that the energy that is making it to slow down. Theorist call this energy "quintessence," , but all this is a theory we don’t know if it really exist and if that was the case we don’t know why it’s there and so the mystery continues. 

Maybe the only theory is that Einstein was wrong but this would affect the expansion of the universe as we know it. In fact this would lead to decide a solution to this dark energy problem. But what it would be? Another gravity theory? If another gravity theory would be the solution. What it would be? There are lot of theories but we can’t prove them at least not we the knowledge we have in our days. I am anxious that someday preferably not too far scientist could be able to solve this whole mystery once and for all, and came with a new theory of gravity if that is the case.

Here is a link to an article that I found interesting about a new method to see gravitation and dark energy: http://hubblesite.org/newscenter/archive/releases/2010/26/full/

Topic of Magnetism

Kermelr Ruperto Justiniano

When we think about physic, we think about strength, we think the action of moving an object, dropping things, etc. In my studies of physics without doubt one of the issues but to draw attention to me as a kid I was curious is the subject of magnetism. When a child sees as certain materials are attracted to each other and one asks, "How that occur?" or "Why that occur?". And here where the physics helped me to understand part of why and how this phenomenon occurs that is so important in life on earth as in many of the artifacts that we use. 

To give a simple definition of what we could say that magnetism is a fundamental force in our nature, which is one of the forces is used in many of the components used and an used such as the compass. Magnetism occurs when when certain charged particles set in motion. We see mostly, but do not know when certain materials attract or repel. There will be seen when they are two magnets, if you put glue on one side or else try to separade and try to unite them more than you do not. This is where true strength of attraction and repulsion. These issues go beyond simply paste or separate things. The magnetism able to help scientists understand atomic structures. 

The area includes many magnetism such as electromagnetism that surrounds what is electricity. These areas were studied years ago simultaneously and noticed that there was a relationship between them. Behaviors were observed that when a magnet as it approached a induce cable is produced or an electric current in the cable (discovered by Michael Faraday). It was also noted that there were internal magnetic fields in materials such as iron (Ernst Weiss), among other things. With all this research is an able to do many simulations and research. Going back fully to the magnetism is a very interesting are the magnetic fields, which also involve electricity in some cases.Una bar magnet or current-carrying wire can influence other magnetic materials without touching them physically because magnetic objects produce a 'field magnetic'. Magnetic fields are usually represented by 'magnetic field lines' or 'lines of force'. At any point, the direction of the magnetic field is equal to the direction of the lines of force. After saying this, I explain the workings of one of the things that after seeing and learning in my class that I decided to take on the task of seeing how the compass works is that an object that looks simple but it is, we can see that is physically behind his invention. 

The compass lets us know according to the place where we stand, to where is north, but, "How this happen?". The compass needle is a needle that magnetism and rotates about an axis. This indicates the direction north and south magnetic pole. The movement of the needle and the sense tell us that we must turn occurs internally and the earth has a magnetic field, where the South Pole of the field is in the North pole of the earth and the North Pole is in the field the South Pole of the earth. The needle and said that this magnet with the North Pole, opposite the South Pole of the earth's magnetic field. As explained earlier the opposite poles attract, for that reason the North pole of the compass is attracted the south pole of the earth's magnetic field which in turn is at the geographic North Pole. This is why we always tell the compass to where the North. Although I have to first admit that physics is not 100% mine, I must say it helps explain many of the situations that you are not even know why or how they occur.

Is the Relativity’s theory of Einstein wrong?

Mileyska Rodriguez Roman

As students we have learned that all this time there does not exist any particle faster than the speed of light, because that was proved experimentally by Albert Einstein. Our studies in physics normally are based on Einstein’s theories; also our world is described and explained by him. The question is what happens if some scientists discover that the theories of Einstein can be wrong? That really there exists a particle faster than light. That's something that according to Einstein's 1905 special theory of relativity, the famous E = m  equation, just doesn't happen. Let’s examine the experiment that some scientists are doing to prove that there exists a particle faster than light and what will happens if it is true.

Who was Einstein? Albert Einstein was a very recognized German physicist who developed the theory of general relativity, affecting a revolution in physics. He received the 1921 Nobel Prize in Physics for his services to theoretical physics, and especially for his discovery of the law of the photoelectric effect. The latter was pivotal in establishing quantum theory within physics. He realized the inadequacies of Newtonian mechanics and his special theory of relativity stemmed from an attempt to reconcile the laws of mechanics with the laws of the electromagnetic field. Those theories mentioned above are only a little part of all the things that Einstein discover and proved experimentally, he was a genius and for this achievement, Einstein is often regarded as the father of modern physics and one of the most prolific intellects in human history. 

What is the theory of the relativity and how it works? The theory of relativity said that the speed of light in a vacuum is constant and an absolute physical boundary for motion. It states that objects will move slower and shorten in length from the point of view of an observer on Earth. This theory is divided in two parts. The first is the Special Theory of Relativity which states that motion and rest are relative. The second is the General Theory of Relativity which applies to particles that accelerate due to gravitation and states that objects continue to move in a straight line in space-time, but we observe the motion as acceleration because of the curved nature of space-time. This theory was confirmed when occur a solar eclipse in 1919 where the light of the stars was deflected by the sun as the light passes through the earth.

We have known all of the past centuries of physics, now it’s time to know what happened to disregard what have been proved in the past by Einstein. A few scientists from Italy made an experiment named OPERA with neutrinos where these particles appear to be faster than the light. Neutrinos are similar to electrons instead they do not have electric charge, they are neutral. Because of that they are not affected by electromagnetic forces. These particles are able to pass through great distances in matter without being affected by it. OPERA is a neutrino detector built in a cavern under the Gran Sasso mount in central Italy. It is called long baseline experiment, which receives neutrinos of the muon type produced by the interactions of 400 GeV protons with the CNGS neutrino beam facility at the CERN laboratory, 454 miles away. The study is based upon the transformation of the muon variety of neutrinos into the tau variety where they are trying to explain the result that the neutrinos appeared to travel faster than the speed of light.

No matter what the CERN prove the velocity of light is constant and is going to be 300,000 km/s every time because this is a natural characteristic. This is not the part of the theory affected because if it were then the experiment would find photons faster than light when that is not the case. Then, what is the case? What happened? The problem is that the speed of light supposed to be a limiting velocity, if the CERN disregard this then it could affect some mathematical computes. For example, a theory predicts that objects that move with a velocity v close to the speed of light c are contracted and their times become longer; the point is that the mathematics of the theory breaks down for values of v = c for instances where the movement of the object is equal to the speed of light. Moreover, it will occur a critical situation because if neutrinos are faster then theories of Einstein will be falsified.

I think that there are many different ways to analyze these particles. If we examine the trajectory of each particle, for example, the neutrino travels in a horizontal path and the light travels in a curvilinear path, then the neutrinos will be faster.  It could be an error of Einstein or the CERN, so they have to keep analyzing all the possible variables experimentally and determine what makes more sense. If Einstein is wrong then it’s the beginning of a new revolutionary of physics.

Plutonium-238 and RTG’s use on “Curiosity” and other NASA robots

Raquel I. Quiñones Acosta

Physics laws, ideas and discoveries started out as simple curiosity of a person or group of persons. A perfect match for my curiosity launched to Mars these past days (November 26, 2011) from Kennedy Space Center, FL. “Curiosity” as the Mars new rover was named, has been set to arrive Mars soil on August 6, 2012. The huge robot weighs five times what the rovers Spirit and Opportunity did. Its mission is to find out whether Mars has or had some sort of life. Studies made, arise the thought of Mars soils possibilities to have microbial life. Something as simple as a salt mixture can create a habitable place for microbial life to take part. This because the levels of deliquescence inside the salt mixtures increase, becoming a source for life on Mars soils as it has been proven to happen on the Atacama Desert and other Mars alike soils on Earth by NASA’s scientists Christopher P. McKay  and Alfonso Dávila among others.  This mission as many other NASA missions has the capability of arising new important discoveries for our generation and the generations to come. 

Curiosity will have the capability to be a field geologist and a laboratory simultaneously. Another interesting fact would be the energy source for the rover. As the other NASA rovers, Curiosity will have solar panels to provide energy and a plutonium battery to maintain all parts of the robot working properly. NASA has employed plutonium material batteries to keep the robots warm and collect data for a longer period of time. Plutonium material batteries can make the robots work for years; and even after 10 years the battery produces 92% of its initial energy, making them a powerful tool on our engineering world. According to Michael Banks from Physics World; Curiosity will have enough energy to fire a laser with a 1067 nm wavelength and a power of 10 MW to deposit 15 mJ of energy onto a millimeter spot of rock to break it down.  Then the robot will have the capacity of analyzing the data to determine chemical composition. 

Focusing on the batteries as the source of energy, basic physics terms explain that a normal battery transforms chemical energy into electric energy. Plutonium material batteries are nuclear batteries that use thermal energy to produce electrical energy. Plutonium-238 has been used for decades in radioisotope thermal generators (RTG’s) and the heat energy or electrical energy produced by them maintains the products working for longer considerable periods of time. Plutonium-238 produces 1 kilowatt of energy per 2 kilograms of mass. In the case of the rover Curiosity this type of battery is indispensable for its proper functioning, but yet very expensive. Still alpha particles responsible for the energy on RTG’s are one of the highest energy sources employed by humanity on the military, space and heart pacemakers, because of the mentioned ability of longer-lasting useful life. Alpha particles are responsible for the high energy nuclear reactions necessary for the robots, landers, rovers and other devices prepared for space studies to last long enough for discoveries farther away from the sun than our planet Earth. Probably physicist Ernest Rutherford never imagined that his studies on alpha particles would have such a large and amazing impact on our actual studies for the search of life on other planets. 

DIGITAL CONTACT LENSES: THE EYES OF THE FUTURE

Yrret Maldonado Ortiz

Envision the idea of being constantly updated with the latest information. At the present time the possibilities are remarkable. An international team of researchers has developed the first working prototype for such a device. In a study published in the Journal of Micromechanics and Microengineering, the researchers from the University of Washington, Seattle, and Aalto University in Finland describe the construction of a computerized single pixel contact lens and demonstrated its safety by testing it on live eyes that showed no adverse side effects.

The prototype contact lens has the capacity of streaming real-time information across the field of vision; potentially providing the wearer with information updates. This device is an example of the integration of devices into miniaturization unconventional substrates. The lens display consists of an antenna to harvest power sent out by an external source, as well as an integrated circuit to store this energy and transfer it to a transparent sapphire chip containing a single blue LED. 

 

One of the mayor challenges the researchers had to face in the design process of generating the contact lens was due to the required small size of the nature of the contact lens and that due to the fact that the human eye  has a minimum focal distance which is at least several centimetre away, therefore objects on a contact lens cannot be resolved, making the information in the lens itself look blurry and out of focus. In order to resolve this problem researcher employed a set of a class of micro-lens known as micro-Fresnel lenses, which focus light by refraction in a set of concentric curved surfaces. Their design allows the construction of lenses of large aperture and short focal length without the mass and volume of material that would be required by a lens of conventional design. Compared to conventional bulky lenses, the Fresnel lens is much thinner, larger, flatter and have shorter focal lenghts, allowing it to focus the projected image onto the retina. Therefore the use of this Fresnel lenses in the design of the contact lens is ideal, because it does not only help solve the problem of the image projection on the retina, making the lens more biocompatible but it also fits the required measurements of volume needed in order to use it in the design of the contact lens.

 

In order for the lens to acquire the necessary energy  for the system to operate without a wired connection, researchers had to developed an CMOS integrated circuit because it meet the terms of the limitation of the design of the lens. Since the strict low power consumption and small footprint requirements in the design of the contact lens prohibited the use of commercially available integrated circuits. Therefore the researchers had to design a custom IC to perform control and radio functions. In order to be able to incorporate the  wireless electronics onto a contact lens. This chip design by the researcher has the ability as the lead researcher Babak Parviz from the university of Washington establish to perform the following tasks: “the conversion of RF power received by the on-lens antenna to a dc-supply voltage, on-chip energy storage sufficient to excite the micro-LED, and generation of an on-chip clock source to duty cycle an LED driver switch.” 

 

Custom designed and fabricated power harvesting and LED driver circuit. (a) Schematic of the CMOS IC architecture and connectivity. (b) Photograph of assembled chip with rectifier and storage capacitor outlined in white, viewed through the polymer substrate. Scale bar is 250μm.

The power management circuitry consists of a ring oscillator, a pulse generator and a passive level shifter. As established by the researchers, “the ring oscillator is powered from the second stage of an eight-stage cascaded rectifier. Each inverter in the three-stage oscillator uses stacked high-threshold devices for low leakage and low-power operation.” As a result, (as the research should) the power consumption of the ring oscillator is less than 500 nW at 1.0 MHz.

The device could overlay computer-generated visual information making it easy to access information instantly from platforms such as mobile phones. The researchers claim that their device will have a wide range of uses; that goes from leisure in its use for gaming devices and navigation system as it can be employed for educational, health application, such as a biosensor and even as an aid to the hearing impaired. Significant improvements are necessary to produce fully functional, remotely powered, high-resolution displays. However the research, data, results and design that wave been obtained by this group of researcher have establish a create stepping stone in the fundamental change of how people access and interact with visual information and how they see the world.

Reference:

A single-pixel wireless contact lens display

A R Lingley1, M Ali2, Y Liao1, R Mirjalili1, M Klonner2, M Sopanen2, S Suihkonen2, T Shen3, B P Otis1, H Lipsanen2 and B A Parviz1

Journal of Micromechanics and Microengineering, Vol.21, Num.12, 125014, 2011

1317_21_12_125014.pdf>

"Digital Contact Lenses Come into Focus." Physicsworld.com. Web. 30 Nov. 2011. .

Future Contact Lenses Can Put Pixels on Our Eyeballs

By Ross A. Lincoln - 12:00 AM - November 26, 2011

http://www.tomsguide.com/us/1-Pixel-Contact-Lens-HUD-implant,news- 13298.html

"Fresnel Lenses." Michigan. Web. 01 Dec. 2011. .

^ "Fresnel lens." Encyclopædia Britannica. 2005. Encyclopædia Britannica Online. 11 November 2005.