Question

When a number of thin convex lenses are placed in contact with one another ,focal length of the combination decreases . why?

Answer 1

Answer:

Explanation:

When two lenses are kept in contact, powers of the lenses are simply added.

Power of a lens is positive for convex lens and negative for concave lens.

Numerically power of a lens is given by

100/f

were f is focal length in centimeters.

As numerically, focal length is same but opposite in size, combined power will be

Zero

i.e. focal length is ∞

i.e. it is just equivalent to plane glass.

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Answer 2

Explanation:

when when two lens are kept in contact power of the lens are simply added

power of a lens are positive convex lens and negative are convent lens

lens is given by 100/ f