Question

The LED emits visible light when its ...........

• A. junction is reverse biased
• B. depletion region widens
• C. holes and electrons recombine
• D. junction becomes hot

Hint:

In LEDs, light is emitted when electrons and holes recombine, releasing energy in the form of photons.

Answer 1

The Correct Option is C

Step 1: Working of an LED.
An LED (Light Emitting Diode) emits light when current flows through it, and electrons recombine with holes in the semiconductor material, releasing energy in the form of photons (light). This process occurs in the forward bias condition.
Step 2: Analyzing the options.

- (1) junction is reverse biased: Incorrect. LEDs emit light when forward biased, not when reverse biased.
- (2) depletion region widens: Incorrect. The depletion region would widen under reverse bias, but this does not cause light emission.
- (3) holes and electrons recombine: Correct. This is the process in which light is emitted in an LED.
- (4) junction becomes hot: Incorrect. While current can cause heating, it’s not the primary reason LEDs emit light.

Step 3: Conclusion.
The LED emits visible light when holes and electrons recombine, corresponding to option (3).