Communication on ground is through electromagnetic waves of wavelength

Options

A. larger than 600 m
B. between 200 and 600 m
C. between 1 and 5 m
D. between `10^(-3)` and 0.1

Answer

To solve the question regarding the communication on the ground through electromagnetic (EM) waves of various wavelengths, we will follow these steps:

### Step-by-Step Solution:

1. **Understanding the Types of Waves**:
- Communication can occur through different types of electromagnetic waves, which are categorized based on their frequencies and wavelengths. The main types relevant to ground communication are:
- Ground waves (also known as space waves)
- Sky waves

2. **Identifying the Wavelength Ranges**:
- We need to identify the wavelength ranges for each type of wave:
- **Sky Waves**: Frequency range is from 3 MHz to 30 MHz. The corresponding wavelength can be calculated using the formula:
\[ \lambda = \frac{c}{f} \]
where \( c = 3 \times 10^8 \, \text{m/s} \) (speed of light).
- For 3 MHz:
\[ \lambda = \frac{3 \times 10^8}{3 \times 10^6} = 100 \, \text{m} \]
- For 30 MHz:
\[ \lambda = \frac{3 \times 10^8}{30 \times 10^6} = 10 \, \text{m} \]
- Thus, the wavelength range for sky waves is from 10 m to 100 m.

- **Space Waves**: Frequency range is from 30 MHz to 300 MHz.
- For 30 MHz:
\[ \lambda = \frac{3 \times 10^8}{30 \times 10^6} = 10 \, \text{m} \]
- For 300 MHz:
\[ \lambda = \frac{3 \times 10^8}{300 \times 10^6} = 1 \, \text{m} \]
- Thus, the wavelength range for space waves is from 1 m to 10 m.

- **Ground Waves**: Frequency range is from 3 GHz to 300 GHz.
- For 3 GHz:
\[ \lambda = \frac{3 \times 10^8}{3 \times 10^9} = 0.1 \, \text{m} \]
- For 300 GHz:
\[ \lambda = \frac{3 \times 10^8}{300 \times 10^9} = 10^{-3} \, \text{m} \]
- Thus, the wavelength range for ground waves is from \( 10^{-3} \, \text{m} \) to \( 0.1 \, \text{m} \).

3. **Conclusion**:
- Based on the calculations, the correct wavelength range for communication on the ground is from \( 10^{-3} \, \text{m} \) to \( 0.1 \, \text{m} \).

### Final Answer:
The communication on the ground is through electromagnetic waves of wavelength between \( 10^{-3} \, \text{m} \) and \( 0.1 \, \text{m} \).

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