Question

Monochromatic light of wavelength 600 nm illuminates two parallel slits 6 mm apart. Calculate the angular deviation of the third order bright fringe (a) in radians, and (b) in degrees.

Answer 1

For mth order bright fringe we have d sin θ = mλ. Now since θ is very small, sin θ ≈ θ = mλ/d.