Does one Candela (SI Unit for lumious intesnity) = lumens per metre squared,
i.e. 1 Cd = 1 lum/m^2
if not, what is the relationship between candela and lumens?
They don't measure the same thing. Lumens measures light output,and candela measures light on a surface.
1 candela= lumen/steradian
Then, in the light intensity equation E=L/r^2, where E is illumination, L is luminous intensity and r is distance, what are the units of each factor?
Candela refers to lumens emitted per steradian in a particular direction by a pointlike source. It is related to the old unit "candle". It does not refer to the lumens hitting a surface per area, that is called illuminance, and is measured in lux.
In the equation E = L/r^2, E (illuminance) is in lux, L is in candelas and r is in meters.
Recommended reading:
http://en.wikipedia.org/wiki/Candela
No, one Candela (Cd) does not equal lumens per square meter (lm/m²). Candela and lumens are two different units used to measure different properties of light.
Candela (Cd) is the SI unit for luminous intensity, which measures the amount of light emitted or received from a light source in a particular direction. It specifically focuses on the brightness or intensity of light in a particular direction.
On the other hand, lumens (lm) is the SI unit for luminous flux, which measures the total amount of visible light emitted by a light source in all directions. It represents the total quantity of light emitted by a source, regardless of the direction in which it is emitted.
To understand the relationship between candela and lumens, we need to consider the concept of solid angle. The solid angle is a measure of the amount of an object's surface area that an observer sees from a particular point. The unit for solid angle is the steradian (sr), which is the SI unit for 3D spatial angle.
The relationship between candela and lumens is as follows:
1 Cd = 1 lm/sr
In other words, if a light source has a luminous intensity of 1 Candela in a particular direction, it means that it emits light with a total luminous flux of 1 lumen spread uniformly over a solid angle of 1 steradian.
So, to convert luminous intensity in Candela to luminous flux in lumens, you need to consider the solid angle over which the light is emitted or received.