Refractive index of lonosphere is

Options

A. zero
B. More than one
C. Less than one
D. One

Answer

To determine the refractive index of the ionosphere, we need to understand its role in communication systems, particularly in relation to satellite communication and signal propagation.

### Step-by-Step Solution:

1. **Understanding Refractive Index**:
The refractive index (n) of a medium is defined as the ratio of the speed of light in vacuum (c) to the speed of light in that medium (v). Mathematically, it is expressed as:
\[ n = \frac{c}{v} \]

2. **Refractive Index of Air**:
The refractive index of air is approximately 1. This means that light travels through air at nearly the same speed as it does in a vacuum.

3. **Ionosphere and Signal Propagation**:
The ionosphere is a layer of the Earth's atmosphere that is ionized by solar and cosmic radiation. It plays a crucial role in radio wave propagation. For effective communication, especially for skywave propagation, the refractive index of the ionosphere should be less than that of air.

4. **Condition for Total Internal Reflection**:
Total internal reflection occurs when light travels from a medium with a higher refractive index to one with a lower refractive index. If the refractive index of the ionosphere were greater than 1, it would not support effective communication as it would lead to total internal reflection.

5. **Conclusion**:
Therefore, for effective satellite communication and to ensure that signals can be transmitted and refracted properly, the refractive index of the ionosphere must be less than 1. This allows for the bending of radio waves back towards the Earth, facilitating long-distance communication.

### Final Answer:
The refractive index of the ionosphere is less than 1.