*Question G9C02:
What is the approximate length of the driven element of a Yagi antenna?*  

*Correct Answer is  B: 1/2 wavelength*  

### AI Response: (may contain errors)  

The correct answer to the question about the approximate length of the driven element of a Yagi antenna is:

**B: 1/2 wavelength**

### Explanation:

1. **Why the correct answer is correct:**
   - The driven element of a Yagi antenna is typically designed to be approximately $1/2$ wavelength long. This length allows the antenna to efficiently radiate and receive radio waves, maximizing its performance. The formula for the length of a dipole antenna, which is similar to the driven element, is given by:
   $$
   L = \frac{468}{f}
   $$
   where:
   - $L$ = length in feet
   - $f$ = frequency in MHz

   For a Yagi, the driven element is often a dipole, hence the $1/2$ wavelength length.

2. **Why the other choices are incorrect:**
   - **A: 1/4 wavelength**: This length is typically used for a quarter-wave vertical antenna, not for the driven element of a Yagi.
   - **C: 3/4 wavelength**: While this length can be used in some specialized antenna designs, it is not standard for the driven element of a Yagi, which is optimized for $1/2$ wavelength.
   - **D: 1 wavelength**: A full wavelength length is generally too long for the driven element of a Yagi and would not provide the desired impedance matching and radiation characteristics.

### Summary:
- The driven element of a Yagi antenna is approximately $1/2$ wavelength long to ensure optimal performance.
- Other lengths (1/4, 3/4, and 1 wavelength) do not provide the same efficiency and are not standard for this type of antenna.