Final answer:
The purpose of a photodiode in reverse bias is to detect light by converting it into an electrical current, and the purpose of an LED in forward bias is to emit light when the current passes through it. Transistors, which are based on similar principles, are used in circuits to amplify or switch electronic signals.
Step-by-step explanation:
Purpose of Photodiode in Reverse Bias and LED in Forward Bias
The purpose of a photodiode when used in reverse bias is to detect light. While in reverse bias, photodiodes are designed to convert light into an electrical current. When light particles (photons) hit the photodiode, they cause the generation of charge carriers that create a current in the reverse direction. Photodiodes are widely used in light-sensing circuits, such as those found in camera sensors and optical fiber communications.
An LED (Light Emitting Diode) in forward bias is used to emit light. When an LED is forward biased, meaning the anode is positive relative to the cathode, it allows current to flow through it, which in turn causes the LED to emit light. The color of the light is determined by the semiconductor material used in the LED. LEDs are prevalent in various lighting applications, from simple indicators to complex display screens.
The functionality of a p-n junction, which is the core of both photodiodes and LEDs, can also be extended to transistors in electric circuits. Transistors can amplify or switch electronic signals, which makes them foundational components in audio amplifiers and computer circuits.