A double-slit experiment gives a fringe width of with an unknown light source

PHYSICS · Single correct · CBSE · Physics · Wave Optics · Wave Optics

Problem

A double-slit experiment gives a fringe width of

2.5\,\text{mm}

with an unknown light source. When the source is replaced by another of wavelength

480\,\text{nm}

, the fringe width becomes

2.0\,\text{mm}

. Determine the wavelength of the original source. (a)

384\,\text{nm}

(b)

720\,\text{nm}

(c)

600\,\text{nm}

(d)

576\,\text{nm}