NEET UG 2017 — Optics

A beam of light from a source $L$ is incident normally on a plane mirror fixed at a certain distance $x$ from the source. The beam is reflected back as a spot on a scale placed just above the source $L$. When the mirror is rotated through a small angle $\theta$, the spot of the light is found to move through a distance $y$ on the scale. The angle $\theta$ is given by

A thin prism having refracting angle ${10}^{o}$ is made of glass of refractive index 1.42. This prism is combined with another thin prism made of glass of refractive index 1.7. This combination produces dispersion without deviation. The refracting angle of second prism should be

The ratio of resolving powers of an optical microscope for two wavelengths ${\lambda }_{1}=4000 Å$ and ${\lambda }_{2}=6000 Å$ is

Two Polaroids ${P}_{1}$ and ${P}_{2}$ are placed with their axis perpendicular to each other. Unpolarised light with intensity ${I}_{0}$ is incident on ${P}_{1}$. A third polaroid ${P}_{3}$ is kept in between ${P}_{1}$ and ${P}_{2}$ such that its axis makes an angle ${45}^{\text{o}}$ with that of ${P}_{1}$. The intensity of transmitted light through ${P}_{2}$ is

Young's double slit experiment is first performed in air and then in a medium other than air. It is found that ${8}^{th}$ bright fringe in the medium lies where ${5}^{th}$ dark fringe lies in air. The refractive index of the medium is nearly