Question

what is Focal length.​

Answer 1

Focal length, usually represented in millimeters (mm), is the basic description of a photographic lens. ... The longer the focal length, the narrower the angle of view and the higher the magnification. The shorter the focal length, the wider the angle of view and the lower the magnification.

Answer 2

Answer:

The focal length of an optical system is a measure of how strongly the system converges or diverges light; it is the inverse of the system's optical power. A positive focal length indicates that a system converges light, while a negative focal length indicates that the system diverges light.