Which of the following statement is wrong regarding a p - n junction diode

Options

A. Diode may illuminate light
B. Diodes are rectifying devices
C. Diodes are unidirectional devices
D. Diodes have three terminals

Answer

To determine which statement is wrong regarding a p-n junction diode, let's analyze the options provided:

1. **Diode has illuminated light**: This statement is correct. Diodes can emit light when they are used as Light Emitting Diodes (LEDs) or can detect light when used as photodiodes.

2. **Diode is a rectifying device**: This statement is also correct. A p-n junction diode allows current to flow in one direction (forward bias) and blocks it in the opposite direction (reverse bias), making it an effective rectifier.

3. **Diode is a unidirectional device**: This statement is correct as well. The primary function of a diode is to allow current to flow in one direction only, thus it is indeed a unidirectional device.

4. **Diode has three terminals**: This statement is incorrect. A p-n junction diode has only two terminals: the anode (P-side) and the cathode (N-side).

Thus, the wrong statement regarding a p-n junction diode is that it has three terminals.

### Step-by-Step Solution:
1. **Identify the statements about the p-n junction diode**: Read through the options provided to understand what each statement claims about the diode.

2. **Evaluate each statement**:
- For the first statement, confirm that diodes can emit or detect light.
- For the second statement, recall the function of diodes in rectifying current.
- For the third statement, remember that diodes allow current to flow in one direction.
- For the fourth statement, check the number of terminals a diode has.

3. **Determine the correctness of each statement**:
- The first three statements are correct based on the properties of diodes.
- The fourth statement is incorrect as a p-n junction diode only has two terminals.

4. **Conclude which statement is wrong**: Based on the evaluation, the statement that a diode has three terminals is wrong.

### Final Answer:
The wrong statement regarding a p-n junction diode is: "Diode has three terminals."