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So why is it that radiation can be harmful? Remember, radiation is any energy released by any object that is then traveling through the air. When you look at a single ray of that energy or radiation, some of those rays will carry much more energy than others. Also, some objects that emit these rays will emit many more rays than other objects. Let’s take, for example, a light bulb and the sun. Both the light bulb and the sunny emit radiation. Each single ray from the sun, however, carries much, much more energy than a single ray from a light bulb. Also, the sun puts out incomprehensibly more rays than does a light bulb. For a fact that the sun’s radiation is potentially dangerous. In the short term, most people watching this video have suffered sunburn, and we also know that with enough exposure over time, people can develop skin cancer later in life from that excessive exposure.
Whereas the light from normal light bulbs cannot harm anyone ever, even if permanently on. Let’s attack that first piece. The amount of energy in a single ray. Well, there’s a certain level of energy per ray over which radiation becomes potentially harmful. For our purposes, let’s call this “the threshold.” It’s all about what happens on a microscopic scale, when that energy gets absorbed by another object. So let’s say you put your hand out in front of a light bulb. Your hand is going to absorb the light energy or the light radiation coming off of that light bulb, right? Otherwise the light would continue to shine through your hand and your hand wouldn’t be opaque. It’d be see-through. Below that threshold, like the light from a normal light bulb, on a microscopic scale, what’s happening is those light rays are encountering the atoms and molecules in the skin of your hand.
And they’re applying a tiny amount of physical force to the molecules. So the molecules shift around a tiny bit, but remain overall intact. So you have the same exact physical makeup, it’s just with a little bit of additional friction. And that’s not that much of a problem. That just means that the energy absorbed from the light ray is dissipated as heat. Notice that’s why a light bulb gets hot when it’s been on for awhile. Now above the threshold of energy, something entirely different happens. Each single ray is too strong to be just stopped by a little physical push and recoil. Instead, the ray will actually damage the atom or the molecule that absorbs it. So think of trying to catch a marble. If another person tosses you the marble, you can catch it quite easily, but if someone actually fires a marble at you from a slingshot and you try to catch it, you’re going to damage your hand.
It’ll enter your hand. Well, in the case of UV light and lower energy cosmic gamma rays, which is fancy terms for the more energetic rays from the sun, when those get absorbed by your skin, they can actually strip electrons off of the surface of water molecules, which makes those water molecules chemically reactive and potentially harmful. In addition to turning water molecules from water into something harmful, it can also potentially directly damage the cells’ infrastructure. So literally physically break a portion of your cell. The most relevant example is that highly energetic rays can damage or even break apart DNA strands. When you start breaking apart the DNA inside of a cell, that can cripple or even kill an individual cell. And this is why radiation is potentially dangerous.
