Question

When an object is placed 20 cm from a concave mirror of focal length 10 cm?

Answer 1

v= -20, solution is mentioned above

Answer 2

Mirror Formula :

           ↓

1/f = 1/u + 1/v ; where

• f = Focal Length.

• u = Distance of object from mirror.

• v = Distance of image from mirror.

Solution :

     ↓

Since object is always kept on negative side that's why v = - 20.

Focal length = 10 cm = 1/2 × Distance of object from mirror.

This proves that object is placed at Center of Curvature.

Similarily, focal length will lie on same plane of object therefore they will also be negative.

→ 1/(- 10) = 1/v + 1/(- 20)

→ - 1/10 = 1/v - 1/20

→ (- 2 + 1)/20 = 1/v

→ - 1/20 =1/v

→ - 20 = v

The negative sign shows that image is formed in same side of object.

Magnification :

          ↓

→ - v/u = - (- 20)/(- 20) = - 1

The negative sign shows that image is below principal axis or INVERTED (Real image).