If a concave and convex lens of equal focus are kept in contact what is the effective focal length?

Answer 1

Effective focal length in #oo#.

The powers of two lenses are simply added when they remain in contact.

For convex lenses, the power of the lens is positive; for concave lenses, it is negative.

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 #oo# i.e. it is just equivalent to plane glass,

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Answer 2

Benjamin Asiedu

When a concave and convex lens of equal focus are kept in contact, the effective focal length is the arithmetic sum of their individual focal lengths.

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Answer from HIX Tutor

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.