joule per square metre is the s.i unit of luminous intensity and temperature.
joule per square metre is the s.i unit of luminous intensity and temperature.
write s.i unit of luminous intensity and temperature?
joule per square metre
luminous intensity should not be confused with another photometric unit, luminous flux, which is the total perceived power emitted in all directions. luminous intensity is the perceived power "per unit solid angle". if a lamp has a 1 lumen bulb and the optics of the lamp are set up to focus the light evenly into a 1 steradian beam, then the beam would have a luminous intensity of 1 candela. if the optics were changed to concentrate the beam into 1/2 steradian then the source would have a luminous intensity of 2 candela. the resulting beam is narrower and brighter, though its luminous flux remains unchanged.
luminous intensity
in general, the luminous intensity of a point on a surface varies by direction; for a lambertian surface, that distribution is defined by the cosine law, with peak luminous intensity in the normal direction. thus when the lambertian assumption holds, we can calculate the total luminous flux, formula_3, from the peak luminous intensity, formula_4, by integrating the cosine law:









































and so
lambert's cosine law