Two identical stinged instruments have a frequency of 100Hz. The tension in one of them is increased by 4%.If they are now sounded together the number of `beat//s` is

Options

A. 1
B. 8
C. 4
D. 2

Answer

D

Explanation

Frequency of string `n=1/(2l)sqrt(T/m)`
`nalphasqrtT`
`n_1/n_2=sqrt(T_1/T_2)`
Given `T_1=T,T_2=T+(Txx4)/100=1.04T,n_1=100,n_2=?`
`100/n_2=sqrt(T/(1.04T)`
`n_2^2=(100)^2xx(1.04)`
`n_2=sqrt(100xx1.04)=102`
`:.` Number of beats = `n_2-n_1=400-392=2 beats//s`