The fringe width is 3.5 mm in Young's double slits experiment for a light of wavelength 700 nm. The fringe width for a light of wavelength 500 mm is:

2.5 mm

The correct answer is Option (1) → 2.5 mm

The fringe width (β) is -

$β=\frac{λD}{d}$

$⇒\frac{β_2}{β_1}=\frac{λ_2}{λ_1}$

$⇒\frac{β_2}{3.5}=\frac{500}{700}$

$⇒β_2=3.5×\frac{500}{700}=2.5mm$