Two coherent sources separated by distance `d` are radiating in phase having wavelength `lambda`. A detector moves in a big circle around the two sources in the plane of the two sources. The angular position of `n=4` interference maxima is given as

Options

A. `sin^(-1)(nlambda)/(d)`
B. `cos^(-1)(4lambda)/(d)`
C. `tan^(-1)(d)/(4lambda)`
D. `cos^(-1((lambda)/(4d)`

Answer

B

Explanation

Path difference `Deltax= d costheta`
For maxima at P `Deltax= nlambda`

`implies nlambda= dcostheta`
`implies theta= cos^(-1)((nlambda)/(d))= cos^(-1)((4lamda)/(d))`