Question

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 m `5 xx 10^(-2)m` towards the slits, the change in fringe width is m `3 xx 10^(-5)m` . If separation between the slits is `10^(-3)m` , the wavelength of light used is
A. `6000Å`
B. `5000Å`
C. `3000Å`
D. `45000Å`

Answer 1

Correct Answer - A
`beta_(1)-beta_(2)=(D_(1))/(d) lambda-(D_(2))/(d) lambda`
`=(lambda)/(d)(D_(1)-D_(2))`
`=(lambda)/(d)(D_(1)-D_(2))`
`=(lambda)/(d)(D_(1)-D_(1)+0.05)`
`=(lambda)/(d)xx0..05`
`:. lambda=(( beta_(1)-beta_(2))d)/(0.05)=(3xx10^(-5)xx10^(-3))/(0.05)`
`=6000 Å`