Question

derive doppler effect and its cases

Answer 1

The Doppler effect is the perceived change in frequency of sound emitted by a source moving relative to the observer: as a plane flies overhead, the note of the engine becomes noticeably lower, as does the siren noise from a fast-moving emergency vehicle as it passes.  The effect was first noted by Christian Doppler in 1842.  The effect is widely used to measure velocities, usually by reflection of a transmitted wave from the moving object, ultrasound for blood in arteries, radar for speeding cars and thunderstorms.  The velocities of distant galaxies are measured using the Doppler effect (the red shift).

Answer 2

The apparent change in frequency of sound wave due to the relative motion of source of sound of sound and observer is called Doppler's effect. When source of sound moves towards observer in rest, then wavelength of sound decreases. The apparent change in frequency is given by f ′ = v v – u s × f .