JEE PYQ: Wave Optics Question 34
Question 34 - 2019 (09 Jan Shift 2)
In a Young’s double slit experiment, the slits are placed 0.320 mm apart. Light of wavelength $\lambda = 500$ nm is incident on the slits. The total number of bright fringes that are observed in the angular range $-30° \leq \theta \leq 30°$ is
(1) 640
(2) 320
(3) 321
(4) 641
Show Answer
Answer: (4)
Solution
For ‘$n$’ number of maximas
$d\sin\theta = n\lambda$
$0.32 \times 10^{-3} \sin 30° = n \times 500 \times 10^{-9}$
$\therefore n = \frac{0.32 \times 10^{-3}}{500 \times 10^{-9}} \times \frac{1}{2} = 320$
Hence total no. of maximas observed in angular range $-30°$
$\leq \theta \leq 30°$
$= 320 + 1 + 320 = 641$
BETA
