Question

An object is placed at a distance of 20 cm in front of a concave mirror of focal length 10 cm. What will be the image distance from the pole of the mirror.

• A. $10\text{cm}$
• B. $15\text{cm}$
• C. $20\text{cm}$
• D. $30\text{cm}$

Answer 1

The correct option is C $20\text{cm}$

Given:
Focal length, f =10 cm
Object position = 20 cm

Using the formula,
R = 2f
R= 20 cm
This menas that the object is placed at the centre of curvature.
When an object is kept at the centre of curvature of a concave mirror, the image is also formed at the centre of curvature.
Hence the image will be inverted and will be formed at the same distance from the pole as the object.