Question

Two plane convex lenes of focal length 10 cm and 20 cm are placed in contact. with each other. The effective focal length of the combination is ​

Answer 1

Answer:

The focal length of a convex lens is always positive. So, the focal of convex lens will be + 0.2 m. The focal length of a concave lens is always negative. Hence, = - 0.1 m

Answer 2

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The focal length of a convex lens is always positive. So, the focal of convex lens will be + 0.2 m. The focal length of a concave lens is always negative. Hence, = - 0.1 m