Radiation (noun, “RAY-dee-a-shun”)
Radiation is one of the ways energy moves from one place to another. Radiation energy moves — or radiates — through space as waves or particles. You might have come across radiation when learning about how heat moves. Heat moves through solids in a process called conduction. Heat also can move by convection, which is the flow of heat through liquids or air. And heat can move via radiation — as energy moving across space. This is how the sun’s energy travels to Earth.
But there are many kinds of radiation. Electromagnetic radiation is a kind of radiation you encounter every day. The light you can see from a candle or light bulb is electromagnetic radiation. So are X-rays and radio waves. The microwaves that heat your food inside a microwave oven are a kind of radiation, too.
Electromagnetic radiation travels as waves, which vary in length. Shorter wavelengths, such as ultraviolet light, X-rays and gamma rays, have a lot of energy and can damage cells. These wavelengths are called ionizing radiation. That’s because they have enough energy to knock negatively charged electrons off atoms.
Longer wavelengths — such as visible light or radio waves — are lower energy and do not damage cells. These wavelengths are called non-ionizing radiation. They do not have enough energy to pop electrons off of atoms.
Another kind of radiation is particle radiation. Some particles — including protons, neutrons, alpha particles and beta particles — travel through space at high speeds. Such particles are often released in a process called radioactive decay. This is when one element converts to a lighter element by shedding a few of its particles. Some of these particles can be high-energy ionizing radiation. Others are lower energy.
High-energy ionizing radiation can be produced in a lab. While this type of radiation damages cells, it can also be used to treat some forms of cancer.
In a sentence
Thunderstorms can release radiation far beyond lightning — they can even produce x-rays and gamma rays.
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