Question

Monochromatic green light of wavelength $5\times {10}^{-7}$ $m$ illuminates a pair of slits $1$ $mm$ apart. The separation of bright lines on the interference pattern formed on a screen $2$ $m$ away is

• A. $0.25$ $mm$
• B. $0.1$ $mm$
• C. $1.0$ $mm$
• D. $0.01$ $mm$

Answer 1

The correct option is C $1.0$ $mm$

$\lambda =5\times {10}^{-7}$ $mm$

$\Rightarrow \lambda =5\times {10}^{-7}\times 1000$

$\Rightarrow \lambda =5\times {10}^{-4}$ $mm$

$d=1$ $mm$

$D=2$ $m$

$\Rightarrow D=2\times 1000$

$\Rightarrow D=2\times {10}^{-3}$ $mm$

$\beta =\frac{D\lambda }{d}$

$\Rightarrow \beta =\frac{2\times {10}^3\times 5\times {10}^{-4}}{1}$

$\Rightarrow \beta =10\times {10}^3\times {10}^{-4}$

$\Rightarrow \beta =1$ $mm$