What is the mechanism of far-infrared rays to produce the heat?
Far infrared ray itself does not hold heat. It is an electric wave called an electromagnetic wave, so it has a property of light, not heat. It directly goes forward in space at the same speed as the light (a velocity of 300 thousand km per second / a speed to revolve around the earth 7.5 times per second) and reaches the surface of materials.
Then, it is easily absorbed into organic substances, such as creatures, and finally turned into heat when absorbed. However, it cannot heat an inorganic substance, such as metal. Even if the far-infrared ray is radiated, it is reflected.
One of the properties contained in light includes “radiation.” Radiation means that light directly reaches the body without running through the air. The speed is as fast as the light, so the heat is transmitted instantly. Radiation allows solar rays to reach the ground and warm the earth by traveling through the airless cosmic space.
Far infrared rays are transmitted by this radiation. Heat only warms the surface of a material, but quite differently from it, a far-infrared ray that is transmitted by radiation warms from inside of the object.
When we bake a fish, we often see the surface gets burned, but the inside is rare. This is because the heat is gradually transmitted to the depth by heat conduction(unlike radiation, in conduction heat runs through inside the material and travels from the high-temperature part to the low-temperature part).
It is often said that charcoal grill provides the most delicious cooking of meat and fish. When charcoal is heated, its surface is slightly covered with ash, and then far infrared ray is generated from oxide contained in the ash, efficiently transmitting the heat.
Resonant absorption phenomena” by far-infrared ray
The skin absorbs far infrared rays that will penetrate into microvessel through fat under the skin. Then, the mechanism of resonant absorption works.
Material has its own frequency. Think of a swing as an example. The swing has its characteristic frequency. If you want to push a swing in which a small child is sitting to make swinging bigger, the swinging cannot become bigger by just applying random force. However, if you push it with the same interval as the frequency of the swing, power is applied in good timing, the swing gradually oscillates wider and wider. This is a principle called sympathetic vibration phenomena, or resonance.
Interestingly, far infrared ray has the same mechanism as this one. The number of vibrations of far infrared rays coincides with the frequency of molecules of creatures, including humans. Molecules of creatures exercise in a complicated way. If far infrared ray conforming to the vibrational frequency of this molecular motion hits creatures, the molecule of the creature resonantly absorbs the energy of far infrared rays and starts hard vibration to raise the temperature.