A beam of light passing from air into a transparent medium, suffers a deviation of $15°$ at the interface, when incident at an angle of $60°$. The speed of light in the medium is

A point source $O$ is placed at a distance of $12.5 \mathrm{cm}$ from a converging lens of focal length $10 \mathrm{cm}$, on its principal axis as shown in the figure. Find the distance at which a diverging mirror of focal length $20 \mathrm{cm}$ should be placed, so that a real image is formed on the source itself.

A screen is placed at a distance of $90 \mathrm{cm}$ from an object. A convex lens forms the image of this object on the screen, when placed at two different locations separated by $30 \mathrm{cm}$ as shown in the figure. Determine the focal length of the lens.

A spherical surface of radius of curvature  separates a rarer and a denser medium. With the help of a neat ray diagram obtain the relationship between the object distance $‘u’$, the image distance $‘v’$, the radius of curvature $‘R’$ and the refractive indices $n_1$ and $n_2$ of the two media, when the object is kept in the rarer medium.

How does the scattering of light vary with the wavelength of different colours of light ?