Four beats are produced on vibrating an unknown tuning fork with another fork of frequency 252 Hz. On loading the unknown fork with little wax and vibrating with another fork 2 beats/s are produced. The frequency of unknown fork before loaded will be

Options

A. 256 Hz
B. 254 Hz
C. 250 Hz
D. 248 Hz

Answer

A

Explanation

`n_(1) = n_(2) +- 4`
`= 252 +- 4 = 256 or 248 Hz`
`n_(1)` is loaded with little wax and sounded with `n_(2)` produces 2 b/s
`n_(1) = n_(2) +- 2`
`= 252 +- 2 = 254 or 250 Hz`
Frequency `n_(1)` before loaded increases by 2
`:. n_(1) = 256 Hz`