What is atmosphere? Draw a neat figure showing the various layer of atmosphere.
The thick layer of air that surrounds the earth'scrust is called atmosphere.
Thermosphere is also called ionosphere. Why?
The lower region of the thermosphere contains ions of nitrogen, oxygen, etc. The gaseous molecules like nitrogen, oxygen, etc. undergo ionization and gives ions due to the effect of UV radiation of sun. Therefore, thermosphere is also called ionosphere.