The distance between object and its two times magnified real image as produced by a convex lens is 45 cm. The focal length of the lens used is __________ cm.

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Solution

Q.
The distance between object and its two times magnified real image as produced by a convex lens is 45 cm. The focal length of the lens used is __________ cm. [2024]

Ans.
(10)

$3 x = 45 cm$ $x = 15 cm$

$u = - 15 cm$ $v = + 30 cm$

By lens formula, $\frac{1}{v} - \frac{1}{u} = \frac{1}{f}$

$\frac{1}{30} - \frac{1}{- 15} = \frac{1}{f}$

$\frac{1 + 2}{30} = \frac{1}{f}$

$f = 10 cm$

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