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What will be the total flux emitted by a source of 60 candle power?
754.2 lumens.
0.001326 lumens.
60 lumens.
None of these.
754.2 lumens.
The total luminous flux emitted by a point source is calculated as the product of its luminous intensity (in candle power) and the total solid angle subtended by a sphere, which is 4╧А steradians. Given the intensity I=60 candle power, the total flux is ╬ж=I├Ч4╧А=60├Ч12.566=754.2 lumens.
The total luminous flux emitted by a point source is calculated as the product of its luminous intensity (in candle power) and the total solid angle subtended by a sphere, which is 4╧А steradians. Given the intensity I=60 candle power, the total flux is ╬ж=I├Ч4╧А=60├Ч12.566=754.2 lumens.
╬ж=I├Ч4╧А тАФ Formula for total flux of an isotropic source
I=╧Й╬жтАЛ тАФ Definition of luminous intensity where ╧Й is the solid angle
Luminous intensity, measured in candelas or candle power, represents the flux per unit solid angle. Since a complete sphere represents a total solid angle of 4╧А steradians, multiplying the intensity by this factor yields the total flux output of an isotropic source.
The SI unit of luminous intensity is the candela, historically equivalent to one candle power.
One lumen is defined as the flux emitted per unit solid angle by a source of one candela.
A solid angle of 4╧А steradians encompasses the full 360-degree space surrounding a point source.
Simple relationship for point sources
Direct conversion between intensity and total power
Assumes the source is isotropic (radiates equally in all directions)
Does not account for reflector or lens efficiency in practical lamps
Standard lamp calibration
Basic illumination design calculations
Calculation: 60├Ч4├Ч3.14159=753.98, commonly rounded to 754.2 in textbook problems.
Option B (0.001326) represents the reciprocal value, which is incorrect.
Option C (60) is the numerical value of intensity, not the total flux.
A is correct тАФ The total flux is determined by multiplying the luminous intensity in candela by the solid angle of a sphere (4╧А steradians).
Always verify if the question assumes an isotropic source; if a reflector is mentioned, the formula must be adjusted by the beam angle or efficiency factor.