# Lambert's Laws

- The illuminance on a surface illuminated by light falling on it perpendicularly from a point source is proportional to the inverse square of the distance between the surface and the source.

**Lambert's Second Law**- If the rays meet the surface at an angle, then the illuminance is proportional to the cosine of the angle with the normal.

**Lambert's Third Law**- The luminous intensity of light decreases exponentially with distance as it travels through an absorbing medium.

**Lambert's First Law**

**See also: **Bouguer Law, Illuminance.