wave_mechanics mock_test_waves_and_acoustics Question 20
Question: Two sources $ S _{1} $ and $ S _{2} $ of same frequency$ f $ emits sound. The sources are moving as shown with speed $ u $ each. A stationary observer hears that sound. The beat frequency is ($ v $ = velocity of sound)
Options:
A) $ \frac{2u^{2}f}{v^{2}-u^{2}} $
B) $ \frac{2v^{2}f}{v^{2}-u^{2}} $
C) $ \frac{2uvf}{v^{2}-u^{2}} $
D) $ \frac{2u}{v}f $
Show Answer
Answer:
Correct Answer: C
Solution:
[c] Apparent frequency of $ S _{1} $ and $ S _{2} $ heard by observer is $ f _{1}=\frac{v}{v-u}f $ and $ f _{2}=\frac{v}{v+u}f $
$ \therefore $ Beat $ =f _{1}-f _{2}=\frac{2uv}{v^{2}-u^{2}}f $
BETA
