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 Å`
B. `4000 Å`
C. `6000 Å`
D. `7000 Å`

Answer

C

Explanation

Fringe width, `beta=(lambdaD)/(d)`
Where `lambda` is the wavelength of light, D is the distance between screen and slits and d is the distance between two slits
`:.Deltabeta=(Deltabetad)/(DeltaD)` (As `lambda` and d are constants)
or `lambda=(Deltabetad)/(DeltaD)`
Substituting the given values, we get
`lambda=((3xx10^(-5)m)(10^(-3)m))/((5xx10^(-2)m))=6xx10^(-7)m=6000 Å`