Question

Can anybody answer these all questions

Answer 1

the centre of the spherical mirror is called pole

Answer 2

pole : the centre of the spherical mirror is called the pole. all the measurements are taken from the pole of the mirror.

centre of curvature: it is the centre of the hollow sphere of which the mirror forms a part. the centre of curvature of a concave mirror is in front of it. where as it lies behind the mirror in case of a convex mirror.

radius of curvature: it is the radius of thw hollow sphere of which the spherical mirror forms a part. it is equal to the distance between the pole and the centre of curvature of a spherical mirror.

principal axis: it is an imaginary straight line passing through the pole and the centre of curvature of the spherical mirror.

-or-

snells law : the ratio of sine of angle of incidence to the sine of angle of refraction is a constant foe the given pair of medium and for a given colour of light.
(the figure given above is for draw a ray diagram for principle focus of concave mirror.)