In Young's double-slit experiment the distance between the slits is 1 mm and that between slit and screen is 1m. If 10th bright fringe is 5 mm away from the central bright fringe, then wavelength of light used will be

Options

A. 5000 Å
B. 6000 Å
C. 4000 Å
D. 8000 Å

Answer

A

Explanation

For nth bright fringe `x=(nlamdaD)/(d)`
here `d=1mm=10^(-3),D=1m,n=10,x=5mm=5xx10^(-3)m`, hence
`lamda=(xd)/(nD)=(5xx10^(-3)xx10^(-3))/(10xx1)=5xx10^(-7)m=5000` Å