Which of the following statements regarding the absorption factor in lighting purposes is correct?
1
It is defined as the ratio of total lumens available after absorption to the total lumens emitted by the source of light.
2
It is defined as the ratio of the candle power before and after absorption of light.
3
It is defined as the ratio of utilisation factor to the depreciation factor.
4
It is defined as the ratio of the change in the brightness after the light has been absorbed by the surface.