If the first minima in Young's double-slit experiment occurs directly in front of one of the slits (distance between slit and screen `D = 12 cm` and distance between slits `d = 5 cm)`, then the wavelength of the radiation used can be

Options

A. 2 cm
B. 4cm
C. 6cm
D. `4/3` cm

Answer

A

Explanation

By Geometry, path difference at .O. for minima should be `(2n-1)(lamda)/(2)`

`therefore S_(2)O-S_(1)O=(2n-1)(lamda)/(2)`
`implies (D^(2)+d^(2))-D=(2n-1)(lamda)/(2)`
`implies (13-12)cm=(2n-1)(lamda)/(2)`
For n=1`implies lamda=2cm`