One can purchase a photodiode from retail stores like Target, Walmart and many more. One can also purchase a photodiode from online websites like eBay or Amazon.

the function of a photodiode is produce some reverse current in the external resistor of circuit.

since the mouse having photodiode installed in them are so fast in response and have less chances of damage.

A light-emitting diode (LED) emits light when an electric current passes through it. A photodiode, on the other hand, generates an electric current when exposed to light. In summary, an LED produces light, while a photodiode detects light.

When Einstein discovered photoelectric effect!