Doppler Effect Applications

Glenda Enid Diaz Acosta

For a given source of a wave and an observer in a fixed distance from this source, the wave emitted from the source will arrive at the observer crest after crest, and there would be a fixed period of the wave; that is the time it takes for one complete cycle of the wave to occur, this period(T) is used to calculate the frequency of the wave given that the period of a wave equals one over the frequency of the same wave(which is also equal to the wavelength of the wave divided by the velocity of sound), and the frequency obtained of the wave will be observed to be the same as the frequency of the wave generated by the source. If then both the source and the observer are in motion relative to each other, then The Doppler Effect takes place. The Doppler Effect is the apparent change in the frequency of a wave, occurring when the source and observer are in motion relative to each other, with the frequency increasing when the source and observer approach each other and decreasing when they move apart from each other. It we have a certain time (T) given we have an apparent change in frequency (f')  of the wave in because of this effect, where f^'=f(1±v_source/v_snd ), in which the v_source is the velocity of the source, v_snd is the velocity of sound in the medium, and f is the frequency of the emitted wave. If we know the frequency of the wave send by the source and the velocity of that source then we can apply this equation and find out the apparent change in frequency, which will allow us to calculate the distance between the source and the observer.

The Doppler Effect has many practical applications for example astronomers use Doppler shifts to calculate precisely how fast stars and other astronomical objects move toward or away from Earth, physicians apply it to measure the rate and direction of blood flow in a patient's body, and also this is the principle used in radar and sonar work; by measuring changes in wavelength and frequency sonar and radar can be used to detect unseen objects and their distance from the observer. Sonar is used to locate under water objects, a transmitter sends out a pulse through the water, and a detector receives its reflection, the time interval between when the pulse is send and received is measured and by applying the Doppler Effect the distance to the reflecting object can be determine using as v_snd  the speed of sound in water. This is used the military to look for submarines and by ocean scientists to find out the depth of water and to map the contours of the ocean bottom, by oceanographers to study everything from the ocean bottom to the waves on top. 

The concept of the Doppler Effect has helped to expand our knowledge of waves. This has helped scientist to hypothesize on the formation of the universe and important theories in physics such as the theory of relativity. It is the basics for the development of the acoustic Doppler velocimeter (ADV) which was develop to measure the velocities in which a fluid flows. In addition it has helped to develop ultrasound machines and  weather radars which use Doppler pulse for meteorological applications, and  also to develop Doppler radars which are used in artifacts as complex as airplanes, and in artifacts as common as police speed guns used to determine the speed of passing vehicles in a common day basics.