STERADIAN

STERADIAN
It is the unit of solid angle or three dimensional angle. Steradian can also be called as squared radian

DEFINITION
One steradian is the angle substended at the center of a sphere at the center of a sphere by a surface area equal to the square of radius of the sphere

MATHEMATICALLY
If area taken on sphere =(radius)^2 Then the angle at center by a surface area is 1 steradian

SYMBOL
It is denoted by 'sr'

EXPLANATION
According to the definition of steradian solid angles in a sphere can be calculated as
................ (Equ. 1)
We know that surface area of the sphere is given by
surface area of sphere = 4πr^2
Putting value in Equ. 1 we get
Solid angle = 4πr^2/r^2
................ (Equ. 2)