List of top Physics Questions on Ray optics and optical instruments asked in DUET

In optical fibres, the refractive index of the core is

When a lens of refractive index $ n_{1} $ is placed in a liquid of refractive index $ n_{2}$ the lens looks to be disappeared only if

For what distance is ray optics a good approximation when the aperture is $4 \,mm$ wide and the wavelength is $500 \,nm$?

Which of the following is true for rays coming from infinity?

Magnification of a compound microscope is $30$. Focal length of eyepiece is $5\, cm$ and the image is formed at a distance of distinct vision $25\, cm$. The magnification of the objective lens is :

A point source of light S, placed at a distance L in front of the centre of a plane mirror of width d, hangs vertically on a wall. A man walks in front of the mirror along a line parallel to the mirror at a distance 2L from it as shown. The greatest distance over which he can see the image of the light source in the mirror is