Question

The angular separation between the central maximum and first order minimum of the diffractions pattern due to a single slit of width 0.25 mm, when light of wavelength 5890 Å is incident normally on the slit, is ________

(a) 7.1 minute

(b) 8.1 minute

(c) 9.1 minute

(d) 10.1 minute

This question was posed to me by my college director while I was bunking the class.

My question comes from Fraunhofer Diffraction in portion Optics of Engineering Physics II

Answer 1

Correct option is (b) 8.1 minute

The best explanation: a = 0.25 mm = 0.25 X 10^-3m, λ = 5890 Å = 5.89 X 10^-7 m.

Angular separation between the central maximum and the first order minimum is given by:

sin θ = \(\frac{\lambda}{a}\) = 0.02356

sin θ ≈ θ

θ = 0.02356 radian

θ = 8.1 minute.