Exams › NEET › Physics

A train moving at a speed of 220 ms⁻¹ towards a stationary object, emits a sound of frequency 1000 Hz. Some of the sound reaching the object gets reflected back to the train as echo. The frequency of the echo as detected by the driver of the train is (speed of sound in air is 330 m/s):

1. 3500 Hz
2. 4000 Hz
3. 5000 Hz
4. 3000 Hz

Correct answer: 4000 Hz

Solution

The Doppler effect is applied twice here: first, the stationary object acts as a listener, and then as a source reflecting the sound back to the moving train. Using the Doppler formula, the frequency detected by the object is 1500 Hz, and the frequency of the echo detected by the train is 4000 Hz.

Related NEET Physics questions

• In stationary waves, nodes are the points where there is:
• How does the sound produced by a vibrating object in a medium reach your ear?
• is the distance between consecutive corresponding points of the same phase, such as crests, troughs, compressions, rarefactions or zero crossings and is a characteristic of both travelling waves and standing waves, as well as other spatial wave patterns.
• An echo is simply a........of sound.
• The condition for constructive interference is path difference should be equal to :
• In a stationary wave:

⚔️ Practice NEET Physics free + battle 1v1 →