Q14 of 123 Page 410

Two concave lenses L1 and L2 are kept in contact with each other. If the space between the two lenses is filled with a material of smaller refractive index, the magnitude of the focal length of the combination

We know that,

Here, d=0, hence F increases.

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A thin lens is made with a material having refractive index μ = 1.5. Both the surfaces of the lens are convex. It is dipped in water (μ = 1.33). It will behave like

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A convex lens is made of a material having refractive index 1.2. Both the surfaces of the lens are convex. If it is dipped into water (μ = 1.33), it will behave like