Light is a form of energy, which is radiated by heated bodies. The light is the part of the radiant energy which produces a sensation (of light) on the human eye.
Luminous flux is the light energy radiated per second from a luminous body in the form of light waves. It is measured in lumen.
Lumen is the unit of luminous flux which is equal to the flux emitted per unit solid angle from a uniform source of one candle power. 1 lumen = 0.0016 watt (approx).
Luminous flux emitted by the sources per unit solid angle in any particular direction is known as the luminous intensity.
The luminous flux falling per unit area on a surface is known as illumination and is expressed in Lumen/m2.
A standard candle is that weighs 1/6 pound of pure spermaceti wax and burning at the rate of 120 grains per hour i.e. 7.776 grams per hour.
The light coming out from a standard candle used as the unit of illuminating power of a lighting source is called standard candle power.
Foot candle or Lumen per square foot is defined as the illumination produced on the inner surface of a hollow sphere of a hollow sphere of radius one foot by a point surface at the center of intensity of one candela. Metre-candle or Lux (Lumen/m^2) is defined as the illumination produced on the inner surface of a hollow sphere of radius one meter by a point surface at the center of uniform intensity of one candela.
Total flux = (4 π × total candle power) Lumens = ( 4 × 3.1421 × 60) Lumens = 754.2 Lumens
Mean Horizontal Candle Power ( M.H.C.P) is the mean of the candle powers in all directions in the horizontal plane passing through the source of light.