Question

In Young's double slit experiment, the two slits are illuminated by light of wavelength $5890$ $Å$ and the angular distance between the fringes obtained on the screen is $0.2^{o}$ . If the whole apparatus is immersed in water then the angular fringe width will be, if the refractive index of water is $\frac{4}{3}$ .

• A. $0.30^{o}$
• B. $0.15^{o}$
• C. $15^{o}$
• D. $30^{o}$

Answer 1

Answer: (B)

Angular fringe width of pattern formed on the screen in Young's double slit experiment, $w_{a}=\frac{\lambda }{d} \, \Rightarrow \, \, w_{a} \propto \lambda $
where, $\lambda $ and $d$ are wavelength of light and slit width, respectively.
$\Rightarrow \frac{\left(w_{a}\right)_{w a t e r}}{w_{a}}=\frac{\left(\lambda \right)_{w a t e r}}{\lambda }=\frac{\lambda }{\left(\mu \right)_{water}\right) \lambda }$
$\Rightarrow \left(w_{a}\right)_{w a t e r}=\frac{0.2 \times 3 \, }{4}=\left(0.15\right)^{o}$