Question

What would be the angular separation between the consecutive bright fringes in Young's double slit experiment with blue green light of wavelength $400\, mm$ ? The separation between the slits is $0.001 \, m$.

• A. $4 \times 10^{-4}\, rad$
• B. $3 \times 10^{-4} \, rad$
• C. $2 \times 10^{-4} \, rad$
• D. $1 \times 10^{-4} \, rad$

Answer 1

Answer: (A)

Given, in Young's double slit experiment,
Wavelength, $\lambda=400 \times 10^{-9} m$
Separation between slits
$d=0.001 m =1 \times 10^{-3} m$
As we know that, $\lambda=d \sin \theta$ and for very small value of $\theta, \sin \theta \approx \theta$
$\therefore \theta=\frac{\lambda}{d}=\frac{400 \times 10^{-9}}{10^{-3}}=4 \times 10^{-4} rad$