To find focal length of a Concave Mirror
1)A thin lens and spherical mirror, each has a focal length of +25cm.

2)A convex lens of focal length f, forms the image of an object equal in size of the object. The object is placed at a distance

3)A parallel beam of light falls on a mirror. All the rays of the beam after reflection, actually intersect at a point. The mirror is a :

4)A real image :

5)An object 2.0 cm in size is placed 20.0 cm in front of a concave mirror of focal length 10.0 cm. Find the distance from the mirror at which a screen should be placed in order to obtain a sharp image. What will be the size and nature of the image formed?