In Young's double experiment , in air interference pattern second minimum is observed exactly in front of one slit. The distance beween the two coherent source is 'd' and the distance between source and screen 'D'. The wavelength of light source used is

Options

A. `(d^(2))/D`
B. `(d^(2))/(2D)`
C. `(d^(2))/(3D)`
D. `(d^(2))/(4D)`

Answer

C

Explanation

Position of a minima in YDSE is given as,
`y = ((2n-1)lambdaD)/(d) "…"(i)`
Here, `y =d/2, n = 2`.
Substituting the values in Eq. (i), we get
`rArr d/2 =D/d ((2 xx 2 - 1)/(2)) lambda rArr d/2 = (D)/(d) 3/2 lambda`
`:. lambda = (d^(2))/(3D)`