Which of the radiation of sun light is used as heat energy

The correct answer is Option (2) → Infra red rays

Infrared rays are called heat waves: they are readily absorbed by the water molecules and other molecules of most materials, which raises their internal energy and so their temperature. The warmth we feel in sunlight comes mainly from its infrared part.

NCERT (2026-27):
Infrared Waves – “… Infrared waves are sometimes referred to as heat waves. This is because water molecules present in most materials readily absorb infrared waves (many other molecules, for example, CO₂, NH₃, also absorb infrared waves). After absorption, their thermal motion increases, that is, they heat up and heat their surroundings.”