Figure shows two coherent sources `S_(1)-S_(2)` vibrating in same phase. `AB` is an irregular wire lying at a far distance from the sources `S_(1)` and `S_(2)`. Let `(lamda)/d=10^(-3)m,/_BOA=0.12^(@)`. How many bright spots will be seen on the wire, including points `A` and `B`

Options

A. 2
B. 3
C. 4
D. more than 4

Answer

b

Explanation

Angular width `(lambda)/(d) = 10^(-3)` (given)
No. of fringes within `0.12^(@)` will be
`n = (0.12 xx 2 pi)/(360 xx 10^(-3)) ~= [2.09]`
The number of bright spots will be three.