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The last kind of radiation is electromagnetic radiation, like X-rays and gamma rays. They are probably the most familiar type of radiation because they are used widely in medical treatments. These rays are like sunlight, except they have more energy. Unlike the other kinds of radiation, there is no mass or charge. The amount of energy can range from very low, like in dental x-rays, to the very high levels seen in irradiators used to sterilize medical equipment.
We say it has no mass and no weight because it has no energy associated with zero velocity. We call this the rest mass, and for photons the rest mass is zero. Ordinary matter like protons and electrons have a rest mass, so we say they have nonzero mass and nonzero energy associated with zero velocity. Protons and electrons respond to gravity the way we expect particles with mass to respond, and they are the reason each of us has mass and weight.