The symbol of a P-N junction diode is shown below. It consists of an arrow that points towards the negative side. The arrow represents the direction of current flow when the diode is forward biased.




Zener diodes are a type of diode that allows current to flow in both directions. The symbol of a Zener diode is similar to that of a P-N junction diode, but it has a bent line on the cathode side.




The symbol of a photo diode is shown below. It has an arrow that points towards the negative side and a circle with a diagonal line inside it. The circle represents the light-sensitive area of the diode.




The symbol of an LED is shown below. It consists of an arrow that points towards the negative side and two horizontal lines on the cathode side. The lines represent the light emitted by the LED.



In conclusion, the symbols of different types of diodes are used to represent their behavior and characteristics in electronic circuits. It is important to understand these symbols to ensure proper functioning of the circuits.