*Question E6F08:
Why are optoisolators often used in conjunction with solid-state circuits that control 120 VAC circuits?*  

*Correct Answer is  C: Optoisolators provide an electrical isolation between a control circuit and the circuit being switched*  

### AI Response: (may contain errors)  

Optoisolators are used to provide electrical isolation between different parts of a circuit. This is particularly important when dealing with circuits that control high voltages, such as 120 VAC, to protect the low-voltage control circuit from high-voltage spikes or faults.

### Explanation:

1. **Correct Answer (C):**  
   - **Electrical Isolation:** Optoisolators use light to transfer signals between two isolated circuits. This means there is no direct electrical connection between the control circuit and the high-voltage circuit. This isolation helps protect sensitive components in the control circuit from high voltages and noise.

2. **Why Other Choices Are Incorrect:**
   - **Choice A:** Optoisolators do not provide a low-impedance link. In fact, they provide high impedance between the input and output to ensure isolation.
   - **Choice B:** Optoisolators are not used for impedance matching. Their primary function is to isolate, not to match impedances.
   - **Choice D:** Optoisolators do not eliminate the effects of reflected light. They use an internal LED and photodetector to transmit signals, and external light does not typically affect their operation.

### Key Points:
- **Function:** Optoisolators use an LED and a photodetector to transmit signals across an isolation barrier.
- **Purpose:** Protects low-voltage circuits from high-voltage circuits by preventing direct electrical contact.
- **Application:** Commonly used in power supplies, microcontroller interfaces, and any application where electrical isolation is necessary for safety and signal integrity.