Utilization of Eectrical Engg Theory

Light:-  

• light is defined as the radiant energy a hot body causing visual sensation on the human eye .

Flux:- 

• it is also known as luminous flux. 
• it is defined as the total quantity of light energy radiated or emitted per second from a luminous body in the form of light waves. 
• it is measured in lumens and is denoted by F .
• it is defined as the rate of uminous energy.
• if the lumens - hour is the luminous o/p of source of light and energy radiated for t hours, then flux is                                                                     F=Q/t

 Light Energy:-

• it is the energy contained in visual radiations in a given time and is expressed in lumen- hour and is denoted by Q

Luminous Efficiency or Radiant Efficiency :- 

• it is defined as the o/p in lumens per watt of the power consumed by the source of light. it is measured in lumens per watt. 
• if a bulb is rated at 500 watt and 250 volts, has an efficiency of 13 lumens/watt. then total flux produced by bulb = 500 * 13  =6500 lumens 

Luminous Intensity:- 

• luminous intensity in any particuar direction is the luminous flux emitted by per unit solid angle by a point sopurce and is denoted by I.                                                                                                      I=F/w   lumens/ steradian or Candle 
• it is the ratio of the brightness of a source of light to that of standard candle. 
• one candle gives out luminous flux of 4 pi lumens in space.
• Thus lumens emitted by one candle source of light is one lumen/steradian.

•    In scientific terms, candle is defined as the luminous intensity in the perpendicular direction of a surface os 1/600,000 sq meter of a full radiator at the temp of freezing platinum under a pressure of 101,325 N/sq. meter.

To Be Continue..........in next slide .......