A toothed wheel is rotated at 120 r.p.m and a post-card is placed aginest the teeth. How many teeth (frequency) must the wheel have to produce a note whse pitch is same as that of a tunning fork of frequency 256/ second ?

Options

A. `256`
B. 120
C. 64
D. 32

Answer

D

Explanation

Here n = no. of teeth `xx ` no. of re/sec.
`256 = (120)/(60) xx m`
m ` = (60 xx 256)/(120) = 12.8 `
Hence the correct choice is (d).