The green light of wavelengths 100A from a narrow slit is incident on a double slit. If the overall separation of 10 fringes on a screen 200cm away is 2cm, find the slit separation?
The wavelength of the green lightλ=100A0
=100×10−10m
=10−8m
The distance between screen and slit is given as D=200cm=2m.
The separation between 10 fringes is given as 2 cm.
Hence, the fringe width is calculated asβ=210cm
=0.2cm
=0.002m
We are asked to calculate the slit width
[d]
The fringe width is calculated as follows β=λDd
⇒d=λDβ
=10−8×20.002m
=10−5m