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An object has image thrice of its origin...

An object has image thrice of its original size when kept at `8 cm` and `16 cm` from a convex lens. Focal length of the lens is

A

8 cm

B

16 cm

C

between 8 cm and 16 cm

D

Less than 8 cm

Text Solution

Verified by Experts

The correct Answer is:
C
`m = pm3 `, as m = `(v)/(u) = (f)/(f + u)`
For virtual image , m = 3
`rArr (f)/(f - 8) = 3 rArr f = 3f - 24 rArr f = 12 cm `
For real image m = -3
`rArr (f)/(f-16) = -3`
`rArr f = -3 f + 48 rArr f = 12 ` cm.
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