Wave Mechanics Beats Question 20
Question: A source of sound gives five beats per second when sounded with another source of frequency $ 100{{s}^{-1}} $ . The second harmonic of the source together with a source of frequency $ 205{{s}^{-1}} $ gives five beats per second. What is the frequency of the source
[CBSE PMT 1995]
Options:
A) $ 105{{s}^{-1}} $
B) $ 205{{s}^{-1}} $
C) $ 95{{s}^{-1}} $
D) $ 100{{s}^{-1}} $
Show Answer
Answer:
Correct Answer: A
Solution:
Frequency of the source = 100 ± 5 = 105 Hz or 95 Hz.
Second harmonic of the source = 210 Hz or 190 Hz.
As the second harmonic gives 5 beats/sec with sound of frequency 205 Hz, the second harmonic should be 210 Hz.
Therefore Frequency of the source = 105 Hz.
BETA
