Question

An object is placed at a distance of 36 cm from a concave mirror of focal length 20 cm. find image distance​

Answer 1

Answer:

Object distance u=−36 cm

Focal length of concave mirror f=−12 cm

Using mirror formula :

v

1

+

u

1

=

f

1

Or

v

1

+

−36

1

=

−12

1

⟹ v=−18 cm

Magnification

h

o

h

i

=

u

−v

Or

10

h

i

=

−10

−(−18)

⟹ h

i

=−18 cm

Image formed is real and inverted.

Answer 2

Answer:

      v = -18cm

Explanation:

object distance - u = -36cm

focal length - f = -12cm

image distance - v

1 / v + 1 / u = 1 / f

1 / v = 1 / f - 1 / u

1 / v = u - f / uf

v = uf / u - f

v = -36 × -12 / -12 + 36

v = 36 × 12 / 24

v = 36 / 2

v = -18cm

Image is formed on the same side of the object