Question

how far should the object is placed of a converging mirror of focal lenght 20cm to form a real image of size 1/4th the size of image.




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Answer 1

Answer:

f = -20cm, m = -1/4 (real image)

We know that

m = - (v/u)

-(1/4) = - (v/u)

u = 4v

so

1/v + 1/u = 1/f

1/v + 1/4v = 1/(-20)

5/4v = - (1/20)

V = - (100/4) = -25 cm

∴ u = 4v

u = 4 × (-25)

= - 100 cm

The object should be placed 100 cm to the left of the mirror. 

Answer 2

It should be 23 hope it helps you