What is called a focal point of a concave mirror ?

What is a concave mirror ?

What is the role of sun rays in finding the focal point of the concave mirror ?

What is the relation between radius of curvature and focal length of a concave mirror ?

Draw a normal at any point of a concave mirror.

An object of size 7 cm is placed at 27 cm in front of a concave mirror of focal length 18 cm. At what distance from the mirror should a screen by placed to obtain a sharp image ? Find size and nature of the image.

An object 4 cm in size, is placed at 25 cm in front of a concave mirror of focal length 15 cm. At what distance from the mirror would a screen be placed in order to obtain a sharp image ? Find the nature and size of the image ?