Several measures of light are commonly known as intensity. These are obtained by dividing either a power or a luminous flux by a solid angle, a planar area, or a combination of the two. The relationships are summarised in the table below:
| Radiometric | Photometric | |
|---|---|---|
| Angular | Radiant intensity, measured in watts per steradian (W/sr) | Luminous intensity, measured in lumens per steradian (lm/sr), or candela (cd) |
| Areal |
Irradiance, measured in watts per square meter (W/m2), called intensity in most branches of physics |
Several quantities measured in lumens per square meter (lm/m2), or lux (lx):
|
| Both | Radiance, commonly called intensity in astronomy and astrophysics (W·sr−1·m−2) | Luminance (lm·sr−1·m−2, or cd/m2) |
Famous quotes containing the words light and/or intensity:
“Her mane falls wild on her forehead,
And the light breeze moves me to caress her long ear
That is delicate as the skin over a girl’s wrist.
Suddenly I realize
That if I stepped out of my body I would break
Into blossom.”
—James Wright (1927–1980)
“The bourgeois treasures nothing more highly than the self.... And so at the cost of intensity he achieves his own preservation and security. His harvest is a quiet mind which he prefers to being possessed by God, as he prefers comfort to pleasure, convenience to liberty, and a pleasant temperature to that deathly inner consuming fire.”
—Hermann Hesse (1877–1962)