In double-slits experiment using light of wavelength 550 nm, the angular width of a fringe formed on a distant screen is 0.2°, What is the spacing between the two slits?

0.158 mm

The correct answer is Option (4) → 0.158 mm

The angular width is,

$θ=\frac{λ}{d}$

Wavelength, $λ=550nm$

Angular width, $θ=0.2=0.2×\frac{\pi}{180}$

$=\frac{\pi}{900}$ radians

$d=\frac{λ}{θ}=\frac{550×10^{-9}×900}{\pi}$

$=0.158mm$