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CUET
Physics
Ray Optics
If f1 = 12 cm, f2 = – 18 cm find the maximum focal length of the combination?
36 cm
34 cm
32 cm
30 cm
$\frac{1}{F} = \frac{1}{f_1} + \frac{1}{f_2} = \frac{1}{12} + \frac{1}{-18} = \frac{3-2}{36}$
$\Rightarrow F = 36cm$