The unit for measuring the rate at which light energy is radiated from a sourse is the ? What? ???

Question

Angstom ... Lumen ... Lux or ... candela

Answer 1

That would be the lumen, but this is weighted according to the spectroscopic sensitivity of the eye.
The equivalent unit for unweighted intensity is:
lumen ↔ watt
lux ↔ watt / m²
candela ↔ watt / sterradian (4π sterradians in a sphere)
Maximum lighting efficacy is 683.002 lumens / watt or 683.002 lux / (watt/m²)

The angstrom is a unit of length corresponding to 0.1 nm.

Answer 2

Not Angstrom. That's a unit of distance, or wavelength.

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