Wave Optics - Result Question 21
21. The Young’s double slit experiment is performed with blue and with green light of wavelengths $4360 \AA$ and $5460 \AA$ respectively. If $x$ is the distance of 4th maxima from the central one, then [1990]
(a) $x$ (blue) $=x$ (green)
(b) $x$ (blue) $>x$ (green)
(c) $x$ (blue) $<x$ (green)
(d) $\frac{x \text{ (blue) }}{x \text{ (green })}=\frac{5460}{4360}$
Show Answer
Answer:
Correct Answer: 21. (c)
Solution:
- (c) Distance of nth maxima, $x=n \lambda \frac{D}{d} \propto \lambda$
As $\lambda_b<\lambda_g \quad \therefore \quad x _{\text{blue }}<x _{\text{green }}$
Fringes with red light are thicker than those for blue light.
$\therefore \lambda _{\text{red }}>\lambda _{\text{blue }}$
