Earth's atmosphere is heated by which of the following process?

Radiation

The correct answer is option 3. Radiation.

Earth's atmosphere is primarily heated by radiation.

Radiation from the Sun is the primary source of heat for Earth's atmosphere. Solar radiation, which consists mainly of visible light and infrared radiation, penetrates the atmosphere and heats the Earth's surface. This heat is then transferred to the surrounding air through processes such as conduction and convection. Additionally, the Earth's surface also emits infrared radiation, which is absorbed by greenhouse gases in the atmosphere, further contributing to the heating of the atmosphere.