Question

Define focus in light ?

​

Answer 1

In Gemitrical optics, afocus also called a image pint,is the point where light rays originating from a point of an object converge.

Hope it's help you

Answer 2

$\huge\colorbox{lime}{Answer}$

The focus is the point, or plane, at which light rays from infinity converge after passing through a lens and traveling a distance of one focal length. In a refractor the first lens through which light from a celestial object passes is called the objective lens.