Two concave lenses L1 and L2 are kept in...

Two concave lenses `L_1 and L_2` 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

A. becomes undefined

B. remains unchanged

C. increases

D. decreases

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HC VERMA-GEOMETRICAL OPTICS-Objective -1

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