Describe how the focal length of a convex mirror can be measured using a convex lens of known focal length.

Describe how the focal length of a convex mirror can be measured using a convex lens of known focal length.

• The apparatus is arranged as shown above
• An object, O is placed in front of a convex lens L and its image formed at C
• The distance LC is measured and recorded.
• The convex mirror whose focal length, f, is required is placed is placed between L and C with its reflecting surface facing the lens.
• The lens is then moved along the axis, OC until a converging beam incident normally on the mirror forms its image at O
• Distance LP is measured

PC = LC – LP thus, f can be determined from f = PC/2