Question

What is Ionosphere? Write any two relevant points.

Hint:

Think of the charged layer of the upper atmosphere and what it does to radio waves.

Answer 1

Step 1: Understand the question:
The question asks what the ionosphere is and wants two relevant points. It carries 2 marks, so one mark is for each point.

Step 2: Define the ionosphere:
The ionosphere is the layer of the upper atmosphere where the air is in a highly ionised state. Sunlight and other radiation break gas atoms into charged particles. Because of this ionised condition, the layer is called the ionosphere. The thermosphere is in this state.

Step 3: Point 1:
The thermosphere is in a highly ionised state and is hence called the ionosphere.

Step 4: Point 2:
This layer reflects radio waves back to the earth. This makes long distance radio communication possible, because the waves bounce between the ionosphere and the ground.

Final Answer:
The ionosphere is the highly ionised layer (the thermosphere) of the upper atmosphere. It reflects radio waves and so makes long range radio communication possible. \[\boxed{\text{Highly ionised layer; reflects radio waves}}\]