Question

A concave lens of focal length 10cm forms an image, which is half of the size that of object. Find the object distance.
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Answer 1

Answer:

-10cm

Explanation:

m=hi/ho=v/u

v/u=0.5

v = 0.5u

from lens formula,

1/f=1/v-1/u

-1/10 = (-1/0.5u)+(1/u)

-1/10 = 1/u

u = -10 cm