The electromagnetic waves of frequency `80 MHz` and `200 MHz`

Options

A. can be reflected by troposphere
B. can be reflected by ionosphere
C. can be reflected by mesosphere
D. cannot be reflected by any layer of earth's atmosphere

Answer

To solve the problem regarding the reflection of electromagnetic waves of frequencies 80 MHz and 200 MHz, we will analyze the properties of the layers of the Earth's atmosphere and their interaction with these frequencies.

### Step-by-Step Solution:

1. **Understanding the Frequencies**:
- We are given two frequencies: 80 MHz and 200 MHz.
- These frequencies are in the range of radio waves, which are commonly used in communication systems.

2. **Identifying the Relevant Atmospheric Layers**:
- The Earth's atmosphere has several layers, but for radio wave communication, the most relevant layers are the troposphere, stratosphere, mesosphere, and ionosphere.
- The ionosphere is particularly important for reflecting radio waves back to Earth.

3. **Reflection Properties of the Ionosphere**:
- The ionosphere can reflect radio waves, but it has a frequency limit.
- Generally, the ionosphere can reflect frequencies up to about 30 MHz effectively. Frequencies above this limit tend to penetrate through the ionosphere.

4. **Analyzing the Given Frequencies**:
- Both 80 MHz and 200 MHz are greater than 30 MHz.
- Therefore, these frequencies will not be reflected by the ionosphere and will instead penetrate through it.

5. **Considering Other Layers**:
- The troposphere and mesosphere do not reflect radio waves in the same way as the ionosphere. They primarily allow radio waves to pass through.
- Since the ionosphere is the only layer that reflects radio waves effectively, and it does not reflect frequencies above 30 MHz, we conclude that the given frequencies will not be reflected by any atmospheric layer.

6. **Conclusion**:
- Since both frequencies (80 MHz and 200 MHz) cannot be reflected by the ionosphere or any other layer of the Earth's atmosphere, the correct answer is that these frequencies cannot be reflected by any layer of the Earth's atmosphere.

### Final Answer:
The frequencies of 80 MHz and 200 MHz cannot be reflected by any layer of the Earth's atmosphere.