Correct Answer - Option 2 : Solid angle
Explanation:
Solid angle is the angle subtended at a point in space by an area, i.e. angle enclosed in the volume formed by numerous lines lying on the surface and meeting at the point. It is usually denoted by symbol ‘ω’ and it is measured in steradian.
\(Solidangle\left( \omega \right) = \frac{{area}}{{radiu{s^2}}} = \frac{A}{{{r^2}}}\)
llumination: It is defined as the luminous flux received by the surface per unit area. It is usually denoted by the symbol E and is measured in lux or lumen/m2 or meter candle or foot candle.
Illumination = (luminous flux/area) lux
The unit of illumination is lux.
Luminous intensity (Luminance) in a given direction is defined as the luminous flux emitted by the source per unit solid angle.
