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. `60xx10^(-4)` cm
B. `10xx10^(-4)` cm
C. `10xx10^(-5)` cm
D. `6xx10^(-5)` cm

Answer

D

Explanation

Distance of nth dark fringe from central fringe
`x_(n)=((2n-1)lambda D)/(2d)`
`therefore x_(2)=((2x2-1)lambdaD)/(2d)=(3lambdaD)/(2d)`
`1xx10^(-3)=(3lambda xx1)/(2xx0.9xx10^(-3)) rArr lambda=6xx10^(-5)cm`