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

Answer

3

Explanation

Say `n` fringes are present in the region shown by `y`
`impliesy=nbeta=(nlamdaD)/(d)`
`implies(lamda)/(D)=tan(0.06^(@))=(0.06xxpi)/(180)=(nlamda)/(d)`
`impliesn=(10^(3)xxpi)/(180)xx0.06=(pi)/(3)gt1`
Hence only one maximum above and below pointO. So total 3 bright spots will be present (including point `O` i.e., the central maxima).