Question

A thin spherical concave mirror has a focal length f. An object in located 10.0 cm in front of the mirror and it is noticed that a real image is formed where the object is located. Calculate the focal length of the mirror.

Answer 1

Answer:

Let us consider a thin spherical concave mirror has a focal length f and we need to find out its value.

Given that, object distance u = 10.0 cm and the real image is formed where the object is located, i.e., image distance v = 10.0 cm. From this we can understand that the object is located at Center of curvature C, then only the real image will form at the same place C with same size.

Using the mirror equation, 1/u + 1/v = 1/f or f = u v/ u+v

Therefore, focal length f = (10.0 cm) (10.0 cm) / 10.0 cm + 10.0 cm = 5.0 cm. and it has positive sign because of it is concave mirror.