Question

Why are infra-red radiations referred to as heat waves? Name the radiations which are next to these radiations in the electromagnetic spectrum having (i) shorter wavelength (ii) longer wavelength. (b) State the conditions under which a microwave oven heats up a food item containing water molecules.

Answer 1

Dear Student,
Infrared waves, with frequencies lower than those of visible light, vibrate
not only the electrons, but entire atoms or molecules in the structure of the
glass. This vibration increases the internal energy and temperature of the structure, which is why infrared waves are often called heat waves. The radiations which are next in the electromagnetic spectrum having shorter wavelength is visible light and that having longer wavelength is microwave.

The natural frequency of the vibration of the water molecules in the food item should be same as that of the frequency of the microwaves .


Regards