Question

A fringe width of a certain interference pattern is $\beta =0.002$ cm. What is the distance of $5^{th}$ dark fringe from centre?

• A. $1\times {10}^{-2}cm$
• B. $11\times {10}^{-2}cm$
• C. $1.1\times {10}^{-2}cm$
• D. $3.28\times {10}^{6}cm$

Answer 1

The correct option is A $1\times {10}^{-2}cm$

Given : $\beta =0.002$ cm

Distance of 5th dark fringe from center $y=(n+\frac{1}{2})\beta$ where $n=4$

$\therefore$ $y=(4+\frac{1}{2})\times 0.002=0.009$ cm

$⟹$ $y\approx 1\times {10}^{-2}$ cm