Question

The rate at which light energy is radiated from a source is measured in which of the following units?

A. Lux
B. Angstrom
C. Candela
D. Lumen

Answer 1

The correct answer is:

D. Lumen

Answer 2

The correct option is D.
Lumen is used to quantify the amount of total light energy that a source is putting out in all direction, thus, it refers to luminous output of a light source. Initial lumen refers to the luminosity of a light when it was first turned on; the luminosity is highest at this point.