A source emits sound with a frequency of 1000 Hz.It and an observer are moving toward each other, each with a speed of 100 m/s.If the speed of sound is 340 m/s, the observer hears sound with a frequency of:
A)290 Hz
B)540 Hz
C)1000 Hz
D)1800 Hz
E)3400 Hz

Question

Quizplus · Accepted Answer

The observed frequency can be calculated using the formula for the Doppler effect when both the source and the observer are moving towards each other: $f' = f \frac{v + v_o}{v - v_s}$, where $f'$ is the observed frequency, $f$ is the source frequency, $v$ is the speed of sound, $v_o$ is the speed of the observer towards the source, and $v_s$ is the speed of the source towards the observer. Plugging in the given values: $f' = 1000 \frac{340 + 100}{340 - 100} = 1000 \frac{440}{240} = 1000 \times \frac{11}{6} = 1833.33 $ Hz, which rounds to 1800 Hz, option D.

A Source Emits Sound with a Frequency of 1000 Hz