Luminous intensity
Luminous intensity is a measure of the energy emitted by a light source in a particular direction.
The SI unit of luminous intensity is the candela (cd).
1 cd is that luminous intensity emitted by a monochromatic light source of frequency 540 × 1012 hertz and that has a radiant intensity in that direction of 1/683 watt per steradian.
| SI light units | ||||
|---|---|---|---|---|
| Quantity | SI unit | Symbol | Notes | |
| Luminous energy | joule | J | ||
| Luminous flux | lumen or (candela · steradian) | lm | also called Luminous power | |
| Luminous intensity | candela | cd | ||
| Luminance | candela / square metre | cd/m2 | also called Luminosity | |
| Illuminance | lux or (lumen / square metre) | lx | ||
| Luminous efficiency | lumens per watt | lm/W | ||
See also
Categories: Physical quantity | Optics