Unit 5: Thermodynamics • Reading Assignment
[1] Radiation is a unique form of heat transfer because it is the only method that does not require matter to travel. While conduction needs direct contact and convection needs a moving fluid, radiation moves through empty space. This energy travels in the form of electromagnetic waves. These waves are similar to the radio waves that carry music to a car or the invisible signals used for Wi-Fi. Because radiation can move through a vacuum, it is the reason why the Earth stays warm even though it is separated from the Sun by millions of miles of empty, cold space.
[2] Every object in the universe, including the human body, is constantly emitting some amount of radiation. This happens because the moving atoms inside an object create electromagnetic waves that carry energy away from the surface. The hotter an object is, the more radiation it gives off. For example, a hot stovetop emits infrared radiation that you can feel as heat on your face even if you aren't touching the burner. If an object gets hot enough, it will even begin to emit visible light, like the glowing orange coils in a toaster.
[3] When radiation waves hit an object, the energy can be absorbed, reflected, or transmitted. If an object is dark or dull, it tends to absorb most of the radiation that hits it. This absorbed energy makes the atoms in the object move faster, which causes the temperature to rise. This is why a black car feels much hotter than a white car after sitting in the sun. The white car reflects more of the radiation away, preventing the energy from being absorbed by the metal.
[4] Light-colored and shiny materials are often used to control radiation for safety and comfort. Firefighters often wear shiny, silver suits when fighting intense fires. These "proximity suits" are designed to reflect the intense infrared radiation away from the firefighter's body so they don't overheat. Similarly, high-tech blankets found in emergency kits are made of a thin, shiny material called Mylar. These blankets work by reflecting your own body's radiation back toward you, trapping your heat and keeping you warm in cold weather.
[5] In the world of physics, understanding radiation helps us explain how energy moves on a galactic scale. It allows us to calculate how much energy the Earth receives from the Sun and how much of that energy we send back into space. By mastering the science of electromagnetic waves, engineers can design everything from better insulation for our homes to heat shields that protect spacecraft as they travel through the solar system.