Rays from the Sun converge at a point $15 \, cm$ in front of a concave mirror. Where should an object be placed so that the size of its image is equal to the size of the object?

Identify the device used as a spherical mirror or lens in the following cases,where the image formed is virtual and erect in each case.
$(a)$ Object is placed between the device and its focus,image formed is enlarged and behind it.
$(b)$ Object is placed between the focus and the device,image formed is enlarged and on the same side as that of the object.
$(c)$ Object is placed between infinity and the device,image formed is diminished and between the focus and optical centre on the same side as that of the object.
$(d)$ Object is placed between infinity and the device,image formed is diminished and between the pole and focus,behind it.

The frequency,wavelength,or speed of light does not change on reflection.

Which symbol is used for the refractive index?

$A$ ray is incident along $ACB$ on a spherical mirror,where $C$ is the centre of curvature. In which direction will the ray be reflected?

The focal length of a concave mirror is $30 \, cm$. Find the position of the object in front of the mirror so that the image is three times the size of the object.