Question

In Young's double slit experiment, light of wavelength lambda passes through the double-slit and forms interference fringes on a screen $1.2 \,m$ away. If the difference between $3^{rd}$ order maximum and $3 ^{rd}$ order minimum is $0.18 \,cm$ and the slits are $0.02 \,cm$ apart, then $\lambda$ is

• A. 1200 nm
• B. 450 nm
• C. 600 nm
• D. 300 nm

Answer 1

Answer: (C)

Distance between
$3^{rd}$ order minima and $3^{rd}$ order maxima is $\frac{\beta}{2}$
$\frac{\beta}{2}=0.18 \,cm $
$\beta=0.36 \,cm $
$\beta=\frac{D \lambda}{d}$
$\therefore \lambda=600\, nm$