If Bilal moves, with a speed equal to 0.5 that of sound, away from a stationary organ producing a sound of frequency 'f', he would probably hear a sound of frequency
- 9.9 f
- 7.7 f
- 66 f
- less than f
- 0.25 f
Explanation
When Bilal moves away from a stationary organ producing a sound of frequency 'f' with a speed equal to 0.5 times the speed of sound, he will hear a sound of lower frequency.
This phenomenon is known as the Doppler effect.
To calculate the frequency of the sound Bilal hears, we can use the following formula:
f' = f * (v + vL) / (v + vS)
Where:
- f' is the frequency of the sound heard by Bilal
- f is the frequency of the sound produced by the stationary organ
- v is the speed of sound
- vL is the speed of Bilal
- vS is the speed of the source (in this case, the stationary organ)
Since Bilal is moving away from the source, vS is negative.
We substitute the values into the formula:
f' = f * (v - 0.5v) / (v - (-v))
Simplifying the equation:
f' = f * (0.5v) / (2v)
f' = f * 0.5 / 2
f' = f * 0.25
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