Question

If an object is placed at a distance of 10 cm in front of a concave mirror of a focal length of 20 cm, the image formed will be ______.

Options

• Real and 20 cm in front of the mirror

• Real and 6.67 cm in front of the mirror.

• Virtual and 20 cm behind the mirror.

• Virtual and 6.67 cm behind the mirror.

Answer 1

If an object is placed at a distance of 10 cm in front of a concave mirror of a focal length of 20 cm, the image formed will be virtual and 20 cm behind the mirror.

Explanation:

Given, f = - 20 cm; u = - 10 cm

Using the formula

`1/"f" = 1/"v" + 1/"u"`

`=> 1/(- 20) = 1/v - 1/10`

`=> 1/10 - 1/20 = 1/v`

`=> 1/v = 1/20`

⇒ v = 20 cm