In an astronomical telescope,how is the focal length of the objective lens compared to the focal length of the eyepiece?

What happens when a light ray incident normally on the surface of a glass slab enters from air into the glass?

$(i)$ Define a real image of an object.
$(ii)$ Name the mirror that:
$(a)$ can give a real as well as a virtual image of an object.
$(b)$ will always give a virtual image of the same size as the object.
$(c)$ will always give a virtual and diminished image of an object.
$(d)$ is used by a doctor in examining teeth.
$(iii)$ With the help of a ray diagram,explain the use of a concave mirror as a solar concentrator.

$A$ plane mirror produces a magnification of

If the angle of incidence on a plane mirror is $30^{\circ}$,what is the angle of reflection (in $^{\circ}$)?

Draw ray diagrams showing the image formation by a convex mirror when an object is placed:
$(a)$ at infinity
$(b)$ at a finite distance from the mirror