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**L=I/S**

**Where,**

I is the luminous intensity and S is the area of the source surface perpendicular to the given direction.

Light illumination is the amount of light illuminating a point on a surface. Illuminating sources can be natural (daylight) or from lamps, lighter, etc.

The definition of Light Illumination determines the amount of light that covers a surface. If Ø is the luminous flux and S is the area of the given surface then the illuminance E is determined by E = ∅/S.

The unit of illumination in SI system is lx, and in foot-pound system it is foot-candle. One lx is the illuminance of 1 m² surface area uniformly lighted by 1 lm of luminous flux. The following drawing explains this definition. One foot-candle is 10.76 lux.

**Example:**

Convert the 5 centimeter candle to various light illumination units.

**Solution:**

centimeter candle = 5

flame = 1161.288

foot candle = 4645.152

lumen/square centimeter = 5

lumen/square foot = 4645.152

lumen/square meter = 50000

lux = 50000

meter candle = 50000

nox = 50000000

phot = 5

watt/square centimeter = 0.007299999999999999