A lens is cut into two equal halves (i) along the principal axis (i) perpendicular to principal axis. What will be the focal length of each half?

Answer 1

The lens equation states that the focal length of a lens formed from two lenses stuck together follows the equation 1/R₁ + 1/R₂ = 1/f . A symmetric lens will have the same R for both sides 2/R = 1/f_original so that R = 2f (the focal length of one side).

Splitting a lens along the central axis does not affect the focal length.

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