For a geostationary satellite orbiting around the earth identify the necessary condition.

Options

A. it must lie in the equatorial plane of earth
B. its height from the surface of earth must be `36000 km`
C. it period of revolution must be `2 pi sqrt(R)/(g)`, where `R` is the radius of earth
D. its period of revolution must be `24 hrs`

Answer

To determine the necessary conditions for a geostationary satellite orbiting around the Earth, we can follow these steps:

### Step-by-Step Solution:

1. **Definition of a Geostationary Satellite**:
A geostationary satellite is one that orbits the Earth at the same rotational speed as the Earth itself. This means that it appears to be stationary relative to a point on the Earth's surface.

2. **Condition of Orbit**:
The first necessary condition is that the satellite's orbit must lie in the equatorial plane. This ensures that the satellite remains directly above the same point on the equator as the Earth rotates.

- **Condition 1**: The orbit must lie on the equatorial plane.

3. **Time Period of Revolution**:
The second condition is that the satellite must have a time period of revolution equal to the rotational period of the Earth, which is 24 hours. This allows the satellite to maintain a fixed position relative to the Earth's surface.

- **Condition 2**: The time period of revolution must be 24 hours.

4. **Height Above the Earth's Surface**:
The third condition is that the satellite must be at a specific height above the Earth's surface to achieve the necessary orbital period. For geostationary satellites, this height is approximately 36,000 kilometers.

- **Condition 3**: The height above the Earth's surface must be approximately 36,000 km.

5. **Conclusion**:
All these conditions must be satisfied for a satellite to be classified as geostationary. Therefore, the necessary conditions for a geostationary satellite are:
- The orbit must lie on the equatorial plane.
- The time period of revolution must be 24 hours.
- The height above the Earth's surface must be approximately 36,000 km.

### Final Answer:
The necessary conditions for a geostationary satellite are:
1. The orbit must lie on the equatorial plane.
2. The time period of revolution must be 24 hours.
3. The height above the Earth's surface must be approximately 36,000 km.

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