Question

an object of size 3 cm is diminished thrice when placed in front of a spherical mirror of focal length 10 cm. calculate the object distance and identify the mirror​

Answer 1

Dear Student,

● Answer -

Object distance = 20 cm

Type of mirror - Convex

◆ Explaination -

# Given -

h1 = 3 cm

h2 = h1/3 = 1 cm

f = 10 cm

# Solution -

As size of image is smaller than size of object, it must be a convex mirror.

Magnification by convex mirror is given by -

M = h2/h1 = -v/u

1/3 = -v/u

u = -3v

Using mirror equation for convex mirror,

1/f = 1/v + 1/u

1/10 = 1/v + 1/-3v

1/10 = 2/3v

v = 2/3 × 10

v = 6.67 cm

But we have,

u = -3v

u = -3 × 20/3

u = 20 cm

Therefore, object distance is 20 cm and mirror is convex mirror.

Thanks for asking..