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.