Question

The outermost layer of earth’s atmosphere is
A. Stratosphere
B. Mesosphere
C. Troposphere
D. Ionosphere

Answer 1

Recall the layers of atmosphere starting from closest to the surface of the earth. In the outermost layer, the temperature increases rapidly. It is one of the layers of the thermosphere.

Complete answer:
We know that earth’s atmosphere is generally divided into four parts. We will discuss each of them depending upon the distance of the layer from the surface of the earth.

Troposphere: This is considered as the first layer of the earth’s atmosphere from its surface. This layer has a thickness of 15 km from the surface of the earth. It is considered the most essential layer of the earth as it contains most of the elementary gases for us to sustain. We should know that all the weather activities like rainfall, thunderstorm and fog happen in this layer of the earth’s atmosphere.

Stratosphere: The stratosphere lies above the troposphere. It extends up to a height 50 km to 55 km above the surface of the earth. It contains the essential ozone gas that prevents harmful radiations to reach the surface of the earth.

Mesosphere: The mesosphere lies above the stratosphere. It extends up to the height of 80 km from the surface of the earth. This layer is considered as a protector from meteorites since the meteorites burn up in this layer and do not reach the surface of earth.

Thermosphere: The Ionosphere is one of the layers of thermosphere. In this layer, the temperature of the air rises rapidly as we move upward. The Ionosphere extends up to a height of 80 km to 400 km and it is considered as the outermost layer of the earth’s atmosphere.

So, the correct answer is option (D).

Note: There exists a very thin layer above the ionosphere known as exosphere. Since it is very thin, we consider the ionosphere as the outermost layer of the earth’s atmosphere. The layers of atmosphere are divided in these categories due to variation of temperature with increasing height.