Question

A laser beam of wavelength 600 nm is incident on two slits that are separated by 0.02 mm. What is the separation between adjacent bright maxima observed on a screen 5 m away?(A) 1.1 mm (B) 0.625 mm (C) 20 mm (D) 15 cm (E) 0.1 mm

Answer 1

Answer:

option D

Explanation:

given,

wavelength = 600 nm

width of separation = 0.02 mm

L = 5 m

for mth order maxima

$d \times \dfrac{y_m}{L}=m\lambda$

for (m+1)th order maxima

$d \times \dfrac{y_{m+1}}{L}=(m+1)\lambda$

now,

$y_m=\dfrac{mL\lambda}{d}$      and

$y_{m+1}=\dfrac{(m+1)L\lambda}{d}$

hence,

$\Delta y = y_{m+1} - y_m$

$\Delta y =\dfrac{L\lambda}{d}$

$\Delta y =\dfrac{5 \times 600 \times 10^{-9}}{0.02 \times 10^{-3}}$

$\Delta y =0.15\ m$

$\Delta y =15\ cm$

hence, the correct answer is option D