A Light Sensor generates an output signal indicating the intensity of light by measuring
the radiant energy that exists in a very narrow range of frequencies basically called "light", and which ranges in frequency
from "Infrared" to "Visible" up to "Ultraviolet" light spectrum. The light sensor is a device that converts this
"light energy" whether visible or in the infrared parts of the spectrum into an electrical signal output. Light sensors are
more commonly known as "Photoelectric Devices" or "Photo Sensors" because they convert light energy (photons) into electricity
(electrons).
Photoelectric devices can be grouped into two main categories, those which generate electricity when illuminated,
such as Photo-voltaics or Photo-emissives etc, and those which change their electrical properties in some
way such as Photo-resistors or Photo-conductors. This leads to the following classification of devices.
