wave_mechanics Beats Question 43
Question: A tuning fork of known frequency 256 Hz makes 5 beats per second with the vibrating string of a piano. The beat frequency decreases to 2 beats per second when the tension in the piano string is slightly increased. The frequency of the piano string before increasing the tension was
[AIEEE 2003]
Options:
A) 256 + 5 Hz
B) 256 + 2Hz
C) 256 ? 2 Hz
D) 256 ? 5Hz
Show Answer
Answer:
Correct Answer: D
Solution:
Suppose $ n _{P}= $ frequency of piano =? $ (n _{P}\propto \sqrt{T}) $
$ n _{f}= $ Frequency of tuning fork $ =256Hz $ x = Beat frequency = 5 bps, which is decreasing (5®2) after clanging the tension of piano wire Also, tension of piano wire is increasing so $ n _{P}\downarrow $ Hence nP? nf = x¯ Wrong nf ? nP= x¯ Correct
Therefore nP = nf ? x = 256 ? 5 Hz.
BETA
