summary
● Semiconductor devices that interact with light can be classified as light-detection devices, light- conversion devices, or light-emitting devices.
● Light is electromagnetic radiation that is visible to the human eye.
● The frequency range of light is as follows:
● Infrared light—less than 400,000 gigahertz
● Visible light—400,000 to 750,000 gigahertz
● Ultraviolet light—greater than 750,000 gigahertz
● Light-sensitive devices include photocells, solar cells, photodiodes, and phototransistors.
● The LED (light-emitting diode) is a light-emitting device.
● LEDs are available in many colors.
● An optical coupler combines a light-sensitive device with a light-emitting device.
● The schematic symbols for light-sensitive devices are as shown here:
● Photocell