Question

20 tuning forks are so arranged in series that each fork gives 4 bets per second with the previous one.The frequency of the 20th fork is three times that of the first. What is the frequency of the first tuning fork?

• A. 60 Hz
• B. 57 Hz
• C. 40 Hz
• D. 38 Hz

Answer 1

Answer: (D)

38 Hz

Since, 20 tuning forks are arranged in series and each fork gives 4 bets per second with the previous one, hence, there are 19 intervals.

Hence number of beats produced is $19\times 4=76$

Let, the frequency of first tuning fork is n. Hence, the last fork has frequency 3n(given).

Therefore, $|n-3n|=76$

$2n=76$

$n=38Hz$