in a two-slit experiment with monochromatic light, fringes are obtained on a screen placed at some distance from the slits. If the screen is moved by `5xx10^(-2)` m towards the slits, the change in fringe width is `3xx10^(-5)`. If the distance between the slits is `10^(-3)`m, calculate the wavelength of the light used.

Options

A. 3000 Ã…
B. 4000 Ã…
C. 6000 Ã…
D. 7000 Ã…

Answer

C

Explanation

Fringe width, `beta=(lambda D)/(d)`
where `lambda`is the wavelength of light, D is the distance between screen and the slits and d is the distance between two slits
` :. triangle beta=(lambda)/(d)triangle D " or " lambda=(triangle beta d)/(triangleD) " " ` (As `lambda` and d are constants)
Substituting the given values, we get
` lambda=((3xx10^(-5)m)(10^(-3)m))/((5xx10^(-2)m))=6xx10^(-7)m=6000 Ã…`