Radiation is the electromagnetic transport of heat energy over space. The majority of the electromagnetic energy emitted by the sun is invisible to us. The frequency of electromagnetic radiation is defined as the number of electromagnetic waves passing through a place per second. Visible light has frequencies between 0.4 and 0.7 microns, infrared between 0.7 and 1000 microns, and radio waves beyond this range.
When sunlight strikes an object that is not transparent, its energy is absorbed either directly or indirectly by molecules in the object's surface. The molecules in the surface layer vibrate with their electrons excited, releasing some of the energy they acquired from the solar photons. This is called absorption. Energy can also be transferred from one molecule to another, which requires more energy than absorption but still less than the original photon. These secondary interactions usually result in more high-frequency vibrations (photons) being released into the surrounding medium, which can then be absorbed by other molecules or reflected back towards the source. Molecules on objects that are not transparent to radiation will absorb it; however, atoms are almost entirely transparent to visible light and most radiation beyond X-rays is absorbed by electrons within the atom. Some materials such as glass have relatively large masses so most of the energy from absorbed radiation is converted into heat rather than light.
The amount of energy that can be transmitted through a given area of material per unit time is called the transmission rate.
Radiation is the movement of heat in the form of visible and non-visible light. The sun is a well-known source of heat for dwellings. Furthermore, low-wavelength, non-visible infrared light can transfer heat directly from heated to colder things. This is called blackbody radiation.
Convection is the movement of heat due to density differences in a fluid or gas. As warm air rises, it becomes cooler and moves away from areas where there are more people or things that are hot. This causes areas near hot objects to feel warmer than other places away from any sources of heat. Convection helps to keep rooms at a constant temperature despite changes in weather outside the house.
Conduction is the movement of heat through a solid object by vibrations of particles within the material. Heat flows from a region with more molecules vibrating faster, toward regions with fewer molecules oscillating rapidly. At room temperature, almost all materials conduct heat, but some conduct it more readily than others. For example, metals such as copper and aluminum conduct heat very well because their atoms move freely around, while wood and plastic don't conduct heat as easily because their molecules bond together.
Evaporation is the change of liquid water into a gaseous state below its boiling point.
When you observe the heat rising from a black-topped road in the middle of a hot summer day, this is an example of radiation from Earth. Heat energy is transported from warmer to colder items (such as the road). As it travels, some of this energy is lost as radiation into space.
In conclusion, heat is transferred through radiation. The most common form of radiation on Earth is infrared radiation. When an object such as a person or a room becomes too warm, the excess heat causes water vapor in the atmosphere to change to its gaseous state. This gas will then leave the planet's surface and be replaced by more cool gas from below. This cycle continues until there is equilibrium between the amount of heat entering and leaving the object.