Question

size of image having focal length 20cm is observed to be reduced tl 13rg of its size at what distance the object has been placed from the mirro what is the nature of image and mirrorr

Answer 1

Answer:As we know, m = - v/u = h₁/h₂

⇒ - v/u = 1/3 h₂/h₂

⇒ u = - 3v

Applying mirror formula,

1/v + 1/u = 1/f, we get

when f = + 20 cm

⇒ 1/v - 1/3v = 1/20

⇒ 3 - 1/3v = 1/20

⇒ 2/3v = 1/20

⇒ 3v = 2 × 20

⇒ v = 2 × 30/3

⇒ v = 40/3 .. (i)

u = - 3v

By putting v value, we get

⇒ u = - 3 × 40/3

⇒ u = - 40 cm.

Object Distance = - 40 cm

If we take f = - 20 cm, value of u will be + 40 cm which is not possible.

m = - v/v

⇒ m = - 40/3/- 40

⇒ m = + 1/3

⇒ m = 0.33 cm

This implies that the nature of the image is erect and diminished.

Nature of Image = Convex Mirror.

Explanation:

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