Ionosphere can reflect which type of waves ?

Options

A. Microwaves
B. Radiowaves
C. X-rays
D. y-rays

Answer

**Step-by-Step Solution:**

1. **Understanding the Ionosphere:**
- The ionosphere is a region of the Earth's upper atmosphere, from about 30 miles (48 kilometers) to 600 miles (965 kilometers) above the surface. It is ionized by solar and cosmic radiation and contains a high concentration of free electrons.

2. **Types of Waves:**
- The question asks which type of waves can be reflected by the ionosphere. The options provided are:
- A) Microwaves
- B) Radio waves
- C) X-rays
- D) Gamma rays (Y-rays)

3. **Properties of Waves:**
- Different types of electromagnetic waves have different frequencies and wavelengths.
- Radio waves have longer wavelengths and lower frequencies compared to microwaves, X-rays, and gamma rays.

4. **Reflection Mechanism:**
- The ionosphere reflects certain types of electromagnetic waves due to the presence of free electrons. When radio waves hit the ionosphere, they cause these electrons to vibrate. This vibration re-radiates the energy back towards the Earth, effectively reflecting the radio waves.

5. **Identifying the Correct Option:**
- Given the properties of the ionosphere and the nature of the waves:
- Microwaves have higher frequencies and are not effectively reflected.
- X-rays and gamma rays have very high frequencies and pass through the ionosphere without being reflected.
- Radio waves, due to their lower frequency, are effectively reflected by the ionosphere.

6. **Conclusion:**
- Therefore, the type of wave that the ionosphere can reflect is **Radio Waves** (Option B).

**Final Answer:**
The ionosphere can reflect radio waves.

---