In a Young's experiment, two coherent sources are placed `0.90mm` apart and the fringes are observed one metre away. If is produces the second dark fringe at a distance of `1mm` from the central fringe, the wavelength of monochromatic light used would be

Options

A. `60 xx 10^(-4)` cm
B. `10 xx 10^(-4)` cm
C. `10 xx 10^(-5)` cm
D. `6 xx 10^(-5)` cm

Answer

D

Explanation

Position of n th dark fringes
`x_(n)= ((2n-1)lambdaD)/(2d)`
`10^(-3)= ((2 xx 2 -1) xx lambda xx 1)/(2 xx 0.9 xx 10^(-3))implies lambda= 6 xx 10^(-5)cm`