Question

How was the Doppler’s effect discovered?

Answer 1

Hint: In this question, we will first know about the scientist who discovered the concept of Doppler’s effect. Further, we will see how this effect was tested and we will get the explanation about the discovery of the effect. Further, we will discuss the Doppler’s effect seen in stars and galaxies.

Complete solution:
As we know about the famous Austrian mathematician and physicist, Christian Doppler. He developed the theory in late 1842 to explain the colors of binary stars.

In this theory he said that the observed frequency of an electromagnetic wave or sound wave depends on the relative speed or velocity of the source and its observer.

Now, this change in frequency is called the Doppler’s effect or the Doppler’s shift .

If we try to understand further, when a sound that is approaching us will look like it is higher than the sound really is. Also, when the sound is going away from us, it will seem lower than its actual pitch.

Further, to test Doppler's theory, the Dutch meteorologist Christoph Ballot in 1843 hired 15 trumpeters with precisely-tuned instruments to play on a selected train as it passed by stationary musicians.

As a result they heard a drop in pitch as the train passed by, just as the scientist Doppler predicted.

Additional information:
As we know that the Doppler red-shift of light that is observed from distant stars and galaxies, tell us the information about the universe is expanding or we can say, moving away from a central point. Now, this allows for the Big Bang Theory, because after a bang occurs all of the matter present moves away from the point of origin.
We know that a redshift in light indicates that the object or the body is moving away from the observer. So, this is called the Doppler shift.

Note:
We should remember that the high or low pitch of sound refers to the high or low frequency of the sound. Also, here we should know the relation between frequency and wavelength i.e., they are inversely proportional to each other; this means that when the frequency of the sound is higher its wavelength is low.