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Convex lens of 10 cm focal length is combined with a concave lens of 6 cm focal length. Find the focal length of the combination. |
15 cm – 15 cm 30 cm – 30 cm |
15 cm |
$ f_1 = 10cm , f_2 = -6cm , F= ?$ $ \frac{1}{F} = \frac{1}{f_1} + \frac{1}{f_2} = \frac{1}{6} - \frac{1}{10} = \frac{5 - 3}{30} = \frac{1}{15}$ $\Rightarrow F = 15cm$ |
