Question

What will be the distance between two slits which, when illuminated by light of wavelength $5000A^o$, produce fringes of width $0.5mm$ on a screen distant $1$ meter from the slits?

• A. ${10}^{-2}$ meter
• B. ${10}^{-3}$ meter
• C. ${10}^{-4}$ meter
• D. ${10}^{-6}$ meter

Answer 1

The correct option is B ${10}^{-3}$ meter

Fringe width is given by $\beta =\frac{D\lambda }{d}$

$⟹d=\frac{D\lambda }{\beta }$

$=\frac{1\times 5000\times {10}^{-10}}{0.5\times {10}^{-3}}$

$={10}^{-3}m$

Hence correct answer is option B.