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. `7000Å`
B. `5000Å`
C. `6000Å`
D. `4000Å`

Answer

C

Explanation

The fringe width `beta` is given by
`beta =(lamdaD)/(2d)` and `beta.=(lamdaD.)/(2d)`
Where `lamda` is the wavelength of light used,
D is the distance of the screen from the two sits and 2d is the separation between two slits
Now `beta-beta.=(lamda(D-D.))/(2d)`
`implieslamda=((beta-beta.)2d)/(D-D.)`
`lamda=((3xx10^(-5))(10^(-3)))/(5xx10^(-2))`
`=0.6xx10^(-6)m=6000Å`