What is the Doppler effect?

Nowadays, a certain phenomenon called "Doppler Effect" has increasingly began to mention. The brilliant opening of the hardworking and, undoubtedly, a talented figure, whose name and is assigned to the surprise invention, not only brought the scientist world fame, but also became a real find, widely used in all sorts of scientific and technical spheres.

The phenomenon claims the following: sound wave (acoustic action) or an electromagnetic radiation wave (optical action) extends in air with a constant rate depending only on the properties of the environment. However, the wavelength and its sound frequency can vary significantly as a result of the position change:

• the source from which the sound comes;

• direct observer.

So, if the observer approaches the source, the frequency of the wave increases, while their distance contributes to lower frequency. "Doppler Effect" is easy to see in action when a car is passing by a man with a lilac included. Suppose it makes not changing the tone of a certain height. When the machine remains fixed relative to a person, his ear perceives the tone, directly published by the lilac. But as soon as the car starts approaching it, the frequency of sound will increase, and the person will hear a loudest tone than the true one. Conversely, when moving the machine, the sound waves will get a low frequency, and it will be heard a quieter tone.

How was the work of the Doppler effect and proved and proved? Based on the results of the observations conducted by the observation of waves on the water surface, Christian Doppler did the assumption that the results obtained can be used and in relation to the waves that apply to the air. On the basis of the wave theory in 1842, he came to this conclusion: with the approach of the light source to the observer, the observed frequency increases, and with the distance, on the contrary, it decreases. Thus, the scientist gave theoretical explanation of the dependence of the frequency of sound and electromagnetic oscillations perceived by the observer, from the direction and speed of the source of these waves relative to the observer itself.

Scientific proof of the effect took place in three years, in 1845. Then the scientist Christian Ballet, Dutchman in origin, conducted the following experiment:

1. In the unclosed railway wagon, he placed one group of trumpets;

2. Other group of trumpeters remained on the platform;

3. It was assumed that the train will pass the platform blizzards;

4. Musicians at this time had to take any tonality;

5. Before the observer, the task was set to write on paper heard.

As a result, it turned out that the way the test was perceived the height of the sound tone, directly dependent on what speed the train moves, as the scientist suggested.

The great discovery of Doppler and today continues to play an unusually important role in various fields of human life. Here are just some possibilities for its use in practice:

• Astronomers with it determined the constant expansion of the universe, as a result of which the stars are moving away from each other.

• Thanks to this effect, it becomes possible to successfully determine the motion parameters of the planets and aircraft vehicles.

• The principle of the operation of ordinary radars, universally used by the traffic police officers in order to determine the speed of the vehicle, is also based on the Doppler opening.

• Finally, it is used for medical purposes - with the help of the ultrasound, the veins and arteries are distinguished during injection.