Radiation is a mode of heat transfer that occurs through electromagnetic waves. Unlike conduction and convection, it does not require a medium to carry the heat energy. The energy is transferred directly in the form of electromagnetic waves.

One of the most familiar examples of radiation is the heat from the sun reaching the Earth. The sun emits a vast amount of electromagnetic radiation, including visible light, infrared radiation, and ultraviolet radiation. When these waves reach our planet, they transfer energy, warming the Earth's surface.

Radiation is also commonly used in various technological applications. For instance, in cooking, microwaves rely on the radiation emitted by the magnetron inside the oven. The electromagnetic waves generated cause the water molecules in the food to vibrate rapidly, generating heat and cooking the food.

Another example is medical imaging, where different types of radiation are utilized. X-rays, for instance, can penetrate through the body and produce an image on a photographic plate or a digital sensor. This allows doctors to diagnose and monitor various medical conditions.