DOPPLER EFFECT

Explanation

The apparent change in the frequency of waves (sound. light etc.) due to the relative motion of the source of waves. and the observer is called Dopple effect. The apparent change in the frequeney of sound heard by an observer, due to the relative motion of the source of sound and the observer is called the Doppler effect in sound
When a source of sound and observer approach each other, the apparent frequency of sound heard by the observer is greater than the true frequency of sound. when they move away from each other, the apparent frequency is less than the true frequency. There is no change in frequency if the relative velocity is at right angles to the line joining the source and
Applications:
(1) In radar, radio waves are used to determine the speed of an aeroplane.
(2) In speed guns used by traffie poli to determine the spesed of cars
(3) In medicine, a Doppler ultrasound test (sonography) uses reflected sound waves to evaluate blood flow through the major arteries and veins of the body. Duplex (or 2D) Doppler, Colour Doppier and Power Doppler are different techniques of the same test.
(4) Doppler effect in light (electvmagetic radiation) le unnd to determine the speed of a star galaxy.