Answer to Question #10736 in Electric Circuits for Akhtar Rasool

Question

Good morning sir what is candela which is intensity of light unit and how can we measure the intensity of light. which instruement we use to measure it?

Answer 1

The candela is the SI base unit of luminous intensity; that is, power emitted by a light source in a particular direction, weighted by the luminosity function (a standardized model of the sensitivity of the human eye to different wavelengths, also known as the luminous efficiency function). A common candle emits light with a luminous intensity of roughly one candela. If emission in some directions is blocked by an opaque barrier, the emission would still be approximately one candela in the directions that are not obscured.
The word candela means candle in Latin, as well as in many modern languages.
Photometer is an instrument for measuring light intensity or optical properties of solutions or surfaces. Most photometers detect the light with photoresistors, photodiodes or photomultipliers. To analyze the light, the photometer may measure the light after it has passed through a filter or through a monochromator for determination at defined wavelengths or for analysis of the spectral distribution of the light.