Which one of the following electromagnetic waves are also referred to as the heat waves?
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → Infrared waves
Infrared waves are called heat waves because they are readily absorbed by water and other molecules in most materials. The absorbed energy increases the thermal (vibrational) motion of the molecules, so the material warms up. This is why infrared lamps are used for heating and physical therapy.
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.”