NEET UG 2018 — Optics

An astronomical refracting telescope will have large angular magnification and high angular resolution, when it has an objective lens of

An object is placed at a distance of 40 cm from a concave mirror of focal length 15 cm. If the object is displaced through a distance of 20 cm towards the mirror, the displacement of the image will be

Unpolarised light is incident from air on plane surface of a material of refractive index $\mu$. At a particular angle of incident $i$ it is found that the reflected and refracted rays are perpendicular to each other. Which of the following options is correct for this situation?

The refractive index of the materiel of a prism is $\sqrt{2}$ and the angle of the prism is ${30}^{o}.$ One of the two refracting surface of the prism is made a mirror inwards, by silver coating. A beam of monochromatic light entering the prism from the other face will retrace its path (after reflection from the silvered surface) if its angle of incidence on the prism is

In Young's double slit experiment the separation $d$ between the slits is $2 mm,$ the wavelength $\lambda$ of the light used is $5896 Å$ and distance $D$ between the screen and slits is $100 cm.$ It is found that the angular width of the fringes is $0.20^{\circ}$. To increase the fringe angular width to ${0.21}^{o}$ (with same $\lambda \text{and} D$) the separation between the slits needs to be changed to