Two sources of sound are placed along the diameter of a circle of radius `R(R gt gt 41)`. How many minima will be heard as one moves along the perimeter of circle.

Options

A. `12`
B. `16`
C. `4`
D. `20`

Answer

A

Explanation

`Delta x = S_(2)P - S_(1)P = 4 lambda sin theta`
For minima: `Delta x = (2n+1)(lambda)/(2)`
`4 lambda sin theta = (2n+1)(lambda)/(2)`
`sin theta = (2n + 1)/(8)`
`n = 0, theta=sin^(-1)(1//8)`
`n=1, theta=sin^(-1)(3//8)`
`n=2, theta = sin^(-1)(5//8)`
`n=3, theta=sin^(-1)(7//8)`
`n=4, theta` is not possible
In quarter circle, `4` minima are head, in entire circle total number of minima `= 12`