Question

when does the focal length of lens decrease ?​

Answer 1

Answer:

As the focal length value decreases, the lens becomes a wide-angle lens, and as the value increases it becomes a telephoto lens. The brightness of a lens is decided by a combination of focal length and lens diameter. If the focal length of two lenses is the same, the lens with the larger diameter will be brighter.

Answer 2

Answer:

focal length is defined as the distance between the principal focus and the pole of the lens, rays meeting the principal axis at a shorter distance decreases the focal length of the lens (principal focus is defined as the point where the parallel rays meet after getting refracted from the lens).

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