Wave Optics - Result Question 8
8. In a double slit experiment, when light of wavelength $400 nm$ was used, the angular width of the first minima formed on a screen placed 1 $m$ away, was found to be $0.2^{\circ}$. What will be the angular width of the first minima, if the entire experimental apparatus is immersed in water? ( $.\mu _{\text{water }}=4 / 3)$
(a) $0.266^{\circ}$
(b) $0.15^{\circ}$
(c) $0.05^{\circ}$
(d) $0.1^{\circ}$
[2019]
Show Answer
Answer:
Correct Answer: 8. (b)
Solution:
- (b) For double slit experiment angular fringe width $\theta_0=\frac{\beta}{D}$
Angular fringe width (in water)
$ \begin{aligned} & \theta_w=\frac{\beta}{\mu D}=\frac{\theta_0}{\mu} \\ & =\frac{0.2^{\circ}}{(\frac{4}{3})}=0.15^{\circ} \end{aligned} $
