6. Intensity Of Light

Intensity is like brightness and is measured as the rate at which light energy is delivered to a unit of surface, or energy per unit time per unit area. The intensity of light is inversely proportional to the square of the distance traveled by the light. This means that as the distance from a light source increases, the intensity of light is equal to a value multiplied by 1/d².

Light intensity refers to the strength or the amount of light produced by a specific lamp source. It is the measure of the wavelength-weighted power emitted by a light source. Different wavelength of light also have more or less energy, depending on whether the wavelength is shorter or longer. So the energy of the light depends on both intensity and wavelength. The Candela (Cd) is the SI base unit of intensity. A common candle emits light with a luminous intensity of roughly 1Cd