If two slits in Young's experiment are 0.4 mm apart and fringe width on a screen 200 cm away is 2 mm the wavelength of light illuminating the slits is

Question

If two slits in Young's experiment are 0.4 mm apart and fringe width on a screen 200 cm away is 2 mm the wavelength of light illuminating the slits is (A) 500 nm (B) 600 nm (C) 400 nm (D) 300 nm

Tardigrade Admin · Accepted Answer

Fringe width W=(D λ/d) Given. d=0.4 mm =0.04 cm, D=200 cm W=2 mm=0.2 cm ∴ 0.2=(200 × λ/0.04) ⇒ λ=400 nm

Q. If two slits in Young's experiment are $0.4 mm$ apart and fringe width on a screen $200 c m$ away is $2 mm$ the wavelength of light illuminating the slits is

500 nm

600 nm

400 nm

300 nm

Fringe width $W = \frac{D λ}{d}$
Given. $d = 0.4 mm = 0.04 c m, D = 200 c m$
$W = 2 mm = 0.2 c m$
$∴ 0.2 = \frac{200 \times λ}{0.04}$
$\Rightarrow λ = 400 nm$

Q. If two slits in Young's experiment are 0.4mm apart and fringe width on a screen 200cm away is 2mm the wavelength of light illuminating the slits is