if decibel is unit of sound(hearing) what is the unit of light(sight)?

Answer 1

candela (Cd) is SI unit. Lumens is cgs unit.

Answer 2

light intensity, which is (on a lightbulb) watts (but watts are the converted unit of energy needed to shine the light). Both measures are related to the amplitude of the sound and light waves.

lambert (La or Lb or L)
a CGS unit of luminance. Luminance is the luminous intensity of a surface, measuring the intensity of the light emitted (or reflected) in all directions per unit of area of the surface. One lambert is the luminance of a surface that emits or reflects one lumen per square centimeter. The lambert is a large unit, and practical measurements tend to be in millilamberts (mLa). A geometric calculation shows that a surface area having an intensity of one candela per square meter emits a total light flux of pi lumens per square meter; as a result, one lambert equals 104/pi = 3183.099 candelas per square meter and 1 millilambert equals 3.183 099 candelas per square meter. The lambert honors the German physicist Johann Lambert (1728-1777), who showed that the illuminance of a surface is inversely proportional to the square of the distance from the light source. There has never been agreement on the symbol for the lambert; La is a good choice because it is unlikely to be confused with any other unit symbol.

Answer 3

Lumens is the measurement for the light output of a mechanical device. Technically since light cannot yet be defined by perimeters we do not have a single unti of measuring it. However you can measure it in intensity, frequency, and polarization. Light can have these following terms used to measure them: Talbots, lumen, lumen second, candela, candela per square metre, lux, lumen per watt, watt per steradian per square metre, extra. It depends on which aspect of light you are trying to measure and under what situation.

Answer 4

lumens