Question

A slit of width 'a' illuminated by white light. The first diffraction minimum for light of wavelength 6500 Å is formed at θ = 30°, then 'a' is (sin 30° = 0.5).

Options

• 6.5 × 10^-5 m

• 0.65 μm

• 1.3 × 10^-5 m

• 1.3 μm

Answer 1

1.3 μm

Explanation:

a sin θ = λ

a = `lambda/(sin 30^circ) = 2lambda = 2 xx 6500 Å`

= 13000 × 10^-10 m

= 1.3 × 10^-6 m

= 1.3 μm