Question

A light emitting diode is (A) a n-p-n type semiconductor with a forward bias

• A. a p-n-p semiconductor with a reverse bias
• B. a p-n-p semiconductor with a forward bias
• C. a p-n semiconductor with a reverse bias
• D. a p-n semiconductor with a forward bias
• E.

Hint:

Forward bias = light ON, reverse bias = light OFF.

Answer 1

Answer: (E)

Concept: A Light Emitting Diode (LED) is a p-n junction device that emits light when current flows through it.

Step 1: Working principle In forward bias:
• Electrons move from n-side to p-side
• Holes move from p-side to n-side
• Recombination occurs at junction
• Energy is released as photons (light)

Step 2: Bias condition
• Forward bias → light emission
• Reverse bias → no current → no light \[ \boxed{\text{LED works only in forward bias}} \]