Question

solve this...........................

Answer 1

$u = - 30cm \\ r = 20cm \\ f = 10cm \\ by \: lens \: formula \\ \frac{1}{f } = \frac{1}{v} - \frac{1}{u} \\ \frac{1}{10} = \frac{1}{v} - \frac{1}{ - 30} \\ \frac{1}{10} = \frac{1}{v} + \frac{1}{30} \\ \frac{1}{v} = \frac{1}{10} - \frac{1}{30} \\ \frac{1}{v} = \frac{3 - 1} {30} \\ \frac{1}{v} = \frac{2}{30} \\ v = 15cm$
image formed is between F and 2F on other side of lens.

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