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

Question

A.Angstrom
B.lux
C.lumen
D.candela

Answer 1

The answer is D. Candela

D. Candela (symbol: cd) is the SI base unit of luminous intensity (that is, power emitted by a light source in a particular direction, with wavelengths weighted by the luminosity function, a standardized model of the sensitivity of the human eye).

A. Ångström, a unit of length equal to 0.1 nanometre

B. Lux (symbol: lx) is the SI unit of illuminance and luminous emittance. It is used in photometry as a measure of the intensity of light, with wavelengths weighted according to the luminosity function, a standardized model of human brightness perception. In English, "lux" is used in both singular and pluraln that luminous flux is adjusted to reflect the varying sensitivity of the human eye to different wavelengths of light

C. The lumen (symbol: lm) is the SI unit of luminous flux, a measure of the perceived power of light. Luminous flux differs from radiant flux, the measure of the total power of light emitted,

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Answer 2

Light Intensity The science of measuring light is called photometry. The three quantities usually measured are the luminous intensity of a source of light; the luminous flux, or the rate at which light energy is radiated from a source; and the illuminance of a surface. Application of the principles of photometry can be helpful in selecting the most suitable type, number, and locations of lamps in a proposed installation. The luminous intensity of a particular source of light is measured by comparing it with the intensity of another source of light that’s selected as a standard. Because wax candles were the most common sources of artificial light when the study of photometry was in its early stages, a candle of specified dimensions and quality was chosen as the standard. (Specifically, a whale oil candle burning at the rate of 7.776 grams per hour was the standard.) The SI metric unit of luminous intensity is the candela. The candela (abbreviated cd) is defined as the luminous intensity, in a given direction, of a surface that emits monochromatic radiation of frequency 540  1012 hertz. An ordinary 100-watt light bulb has an intensity of about 130 cd. The rate at which light energy is radiated from a source of light is called the luminous flux, and the unit of luminous flux is the lumen. For example, suppose that a candle with a light intensity of 1 candela at the tip of the flame is placed in the center of a hollow sphere with a radius of 1 meter. It’s assumed that the intensity of the source is the same in all directions. Therefore, light energy is radiated to each portion of the inside surface of the sphere at the same rate. The luminous flux on any portion of this surface with an area of 1 square meter is 1 lumen.

Answer 3

C.Lumen

Answer 4

candela