For example, UV light from the sun is known to cause skin cancer, so what makes it different from the visible spectrum (other than that we can’t see it)? Furthermore, does the spectrum gradually become more harmful, or is it a sudden jump to being harmful?
In: Physics
As you move from one end of the spectrum to another, there is a gradual energy increase. Basically, red light (low end) has a longer wavelength than blue light (high end), so to make the wave oscillate faster in blue light, you need more energy. The shorter the wavelength is, the more energy is packed in it. This, coupled with intensity, can eventually cause burns or ionizing radiation. Notably, you *could* do that with visible light. The difference is that it often just bounces off our skin or gets dissipated as heat, instead of penetrating our cells. UV light has just enough energy to burn us, and to alter our DNA and cause cancer.
The higher you go, the more energy there is. For example, if you keep going high above UV rays, you eventually find X-rays and gamma rays, both of which can cause serious harm if you’re exposed to them for a long time unprotected. The atmosphere and Earth’s magnetic field both shield us from gamma rays and stuff in that range that is floating about in space. On Earth, this same radiation damage is the reason X-ray technicians (who are working with X-ray machines all day every day) need to go in a separate room while you, only there to get your one X-ray, don’t have to because you’re only exposed for a few seconds. The damage comes from: frequency/wavelength, duration of exposure, intensity of the electromagnetic radiation.
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