Question

In Young’s double-slit experiment, the two parallel slits are made one millimeter apart and a screen is placed one meter away. What is the fringe separation when blue-green light of wavelength 500 nm is used?

(a) 0.5 mm

(b) 50 mm

(c) 0.25 mm

(d) 25 mm

I have been asked this question in a job interview.

Question is from Wave Optics in section Wave Optics of Physics – Class 12

Answer 1

Right option is (a) 0.5 mm

Best explanation: Fringe width is given as:

β = \(\frac {D\lambda }{d}\).

So β = \(\frac { (1 \times 500 \times 10^{-9} ) }{(10^{-3})}\)

β = 0.5 mm

Therefore, the fringe separation when blue-green light of wavelength 500 nm is used is 0.5 mm.