Two monochromatic (wavelength = a/5) and coherent sources of electromagnetic waves are placed on the x-axis at the points (2a,0) and (-a,0). A detector moves in a circle of radius `R(gtgt2a)` whose centre is at the origin. The number of maxima detected during one circular revolution by the detector are

Options

A. 60
B. 15
C. 64
D. none

Answer

A

Explanation

For point `P,Deltax=3a=15lamda` and at point Q it is also `15 lamda` somewhere at point B, it it zero thus in half part of the circle available maxima
`15xx2=30`
Thus total maxima `=2xx30=60`