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

Options

A. 4500 Å
B. 5000 Å
C. 5500 Å
D. 6000 Å

Answer

D

Explanation

Fringe width `beta=(lamdaD)/d`
Where D is the distance between slit and the screen, d is the distance two slits, `lamda` is the wavelength of light.
`Deltabeta=(lamdaDeltaD)/d`
or, `lamda=(Deltabetad)/(DeltaD)=(10^(-3)xx0.03xx10^(-3))/(5xx10^(-2))=(10^(-3)xx3xx10^(-5))/(5xx10^(-2))`
= `6xx10^(-7)m=6000Å`.