Q.
While conducting Young's double slit experiment it was noted that fringe width with light of wavelength 6000A˚ was 3mm . If the experiment is repeated but this time wavelength of light used is 4000A˚ , what will be the new fringe width?
fringe width β=dλD
Where λ is the wavelength of light, D is distance between
slits and the screen, d is distance between the two slits.
As D and d remain the same, β∝λ
Or ββ′=λλ′ or β′=λλ′β
Substituting the given values, we get β′=6000Å4000Å×3mm=2mm