*Question G6B08:
How is an LED biased when emitting light?*  

*Correct Answer is  D: Forward biased*  

### AI Response: (may contain errors)  

An LED (Light Emitting Diode) emits light when it is **forward biased**. Here's why:

1. **Correct Answer: Forward biased**
   - When an LED is forward biased, current flows through it, allowing electrons to recombine with holes in the semiconductor material. This recombination releases energy in the form of light. The forward bias condition is essential for the LED to emit light.

2. **Why the other choices are incorrect:**
   - **A: In the tunnel-effect region**  
     - The tunnel-effect region is related to tunnel diodes, not LEDs. Tunnel diodes operate based on quantum tunneling, which is not the mechanism by which LEDs emit light.
   - **B: At the Zener voltage**  
     - The Zener voltage is a characteristic of Zener diodes, which are designed to operate in reverse bias to regulate voltage. LEDs do not operate at a Zener voltage.
   - **C: Reverse biased**  
     - In reverse bias, the LED does not conduct current under normal conditions and therefore does not emit light. Reverse biasing an LED can lead to breakdown and damage.

3. **Useful Rule of Thumb:**
   - For an LED to emit light, it must be connected in a circuit such that the anode is at a higher potential than the cathode, allowing current to flow through the LED in the forward direction. This is the forward bias condition.