What is a prism?

Draw a labelled ray diagram to locate the image of an object formed by a convex lens of focal length $20 \, cm$ when the object is placed $30 \, cm$ away from the lens.

The image formed by a convex mirror is only one-third of the size of the object. If the focal length of the mirror is $12 \, cm$,the image formed will be

In a diagram,show the following for both a convex mirror and a concave mirror:
$(i)$ Principal axis
$(ii)$ Pole
$(iii)$ Focus
$(iv)$ Centre of curvature
$(v)$ Radius of curvature

Give the relationship of magnification with focal length of a spherical mirror.

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.