The parts of the electromagnetic spectrum with wavelengths shorter than visible light are more dangerous to humans, and the danger gets more serious the shorter the wavelength. Ultraviolet radiation is part of the sun’s rays and it penetrates into the skin. The energy in the radiation can cause changes to the DNA in skin cells. These changes to DNA can sometimes lead to skin cancer. X-rays penetrate through the soft tissue of the body until they reach the bone. This is why X-rays are used by doctors to see broken bones.
X-rays are even more harmful to DNA, which is why pregnant women should avoid them. Gamma rays can penetrate right through the body and are also very dangerous to humans. Gamma rays can only be stopped by 15 cm of solid, heavy lead.
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