The Doppler Effect Video Lessons

Concept

Problem: An opera singer in a convertible sings a note at 600 Hz while cruising down the highway at 100 km/h . The speed of sound n the air is 343 m/s. A) What is the frequency heard by a person standing beside the road in front of the car?B) What is the frequency heard by a person standing beside the road behind the car?

FREE Expert Solution

The frequency detected due to the Dopler's effect is given by:

$\overline{){{\mathbf{f}}}_{{\mathbf{D}}}{\mathbf{=}}\frac{\mathbf{v}\mathbf{±}{\mathbf{v}}_{\mathbf{D}}}{\mathbf{v}\mathbf{±}{\mathbf{v}}_{\mathbf{s}}}{{\mathbf{f}}}_{{\mathbf{s}}}}$, where v is the velocity of the wave in the air, vD is the velocity of the detector, vs is the velocity of the source, and fs is the frequency of the source.

A)

In this problem, we consider the car to be the source and the person standing beside the road in from of the car to be the detector.

Since the person is standing, his velocity, vD = 0.

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Problem Details

An opera singer in a convertible sings a note at 600 Hz while cruising down the highway at 100 km/h . The speed of sound n the air is 343 m/s.

A) What is the frequency heard by a person standing beside the road in front of the car?

B) What is the frequency heard by a person standing beside the road behind the car?