Define Candle Power

Candlepower is an outdated unit of measurement used to express the luminous intensity of a light source, measured in candles. It was replaced by the candela (cd) in the International System of Units (SI) in 1948.

Candlepower was originally defined as the luminous intensity of a standard candle made of spermaceti wax burning at a defined rate. The term "candlepower" was derived from this definition, as it represented the brightness of a candle flame in a particular direction.

However, candlepower was later redefined to represent the luminous intensity of a light source in terms of the light it emitted in a specific direction. This definition varied depending on the type of lamp or light source being measured, which made it difficult to compare the brightness of different light sources.

As a result, the candela (cd) was adopted as the official unit of measurement for luminous intensity in the SI. The candela is defined as the luminous intensity, in a given direction, of a source that emits monochromatic radiation of frequency 540 × 1012 hertz and that has a radiant intensity in that direction of 1/683 watt per steradian.

In summary, candlepower is an outdated unit of measurement used to express the luminous intensity of a light source in terms of the brightness of a standard candle flame. It was replaced by the candela (cd) in the International System of Units (SI) in 1948.