A siren emits a sound wave with frequency f0. The graph shows the frequency you

Question

A siren emits a sound wave with frequency f0. The graph shows the frequency you hear as you stand at rest at x = 0 on the x-axis. Which is the correct description of the siren's motion? It moves from left to right and passes you at t = 2 s. It moves from right to left and passes you at t = 2 s. It moves toward you for 2 s but doesn't reach you, then reverses direction at t = 2 s and moves away. It moves away from you for 2 s, then reverses direction at t = 2 s and moves toward you but doesn't reach you.

Explanation / Answer

Option D is the correct answer.

Here is the explanation

in the first two seconds.
As the siren moves away from you apparent freqyency hear by you is less than original frequency.

Apply Doppler's effect,
f = fo*V/(V + Vs) ===> f < fo

V ---> velocity of sound

Vs---> veloity of siren

After 2 seconds
As the siren moves towards you apparent freqyency hear by you is greater than original frequency.
Apply Doppler's effect,
f = fo*V/(v - Vs) ===> f > fo

V ---> velocity of sound

Vs---> veloity of siren

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