*Question E9F06:
What is the approximate physical length of an air-insulated, parallel conductor transmission line that is electrically 1/2 wavelength long at 14.10 MHz?*  

*Correct Answer is  C: 10.6 meters*  

### AI Response: (may contain errors)  

To determine the physical length of an air-insulated, parallel conductor transmission line that is electrically 1/2 wavelength long at 14.10 MHz, we need to use the formula for the wavelength in free space and then adjust for the electrical length.

### Step-by-step Explanation:

1. **Calculate the Wavelength in Free Space:**

   The wavelength $\lambda$ in meters for a frequency $f$ in MHz is given by:

   $$ \lambda = \frac{300}{f} $$

   For $f = 14.10$ MHz:

   $$ \lambda = \frac{300}{14.10} \approx 21.28 \text{ meters} $$

2. **Determine the Physical Length for 1/2 Wavelength:**

   Since we want the physical length for 1/2 wavelength:

   $$ \text{Physical Length} = \frac{\lambda}{2} $$

   Substituting the value of $\lambda$:

   $$ \text{Physical Length} = \frac{21.28}{2} \approx 10.64 \text{ meters} $$

   This rounds to 10.6 meters, which matches choice C.

### Why the Correct Answer is Correct:

- **Choice C (10.6 meters):** This is the correct answer because it accurately represents the physical length of a 1/2 wavelength transmission line at 14.10 MHz, calculated using the formula for wavelength in free space.

### Why the Other Choices are Incorrect:

- **Choice A (7.0 meters):** This is too short for a 1/2 wavelength at 14.10 MHz. It does not match the calculated value.
  
- **Choice B (8.5 meters):** This is also too short and does not correspond to the calculated 1/2 wavelength.

- **Choice D (13.3 meters):** This is too long for a 1/2 wavelength at 14.10 MHz and exceeds the calculated value.

By understanding the relationship between frequency and wavelength, and how to calculate the physical length of a transmission line, you can accurately determine the correct length for a given frequency.