Wave Mechanics Beats Question 18
Question: A tuning fork of frequency 480 Hz produces 10 beats per second when sounded with a vibrating sonometer string. What must have been the frequency of the string if a slight increase in tension produces lesser beats per second than before
[NCERT 1984]
Options:
A) 460 Hz
B) 470 Hz
C) 480 Hz
D) 490 Hz
Show Answer
Answer:
Correct Answer: B
Solution:
If suppose nS = frequency of string $ =\frac{1}{2l}\sqrt{\frac{T}{m}} $ nf = Frequency of tuning fork = 480 Hz x = Beats heard per second = 10 as tension T increases, so nS increases () Also it is given that number of beats per sec decreases (i.e.
x¯) Hence nS ? nf = x¯ …
(i) Wrong nf ? nS = x¯ …
(ii) Correct
Therefore nS = nf ? x = 480 ? 10 = 470 Hz.
BETA
