calcium into their photoreceptors. In fact, Superman is shown as picking up a lot of different frequencies of light, and so has to have a lot of materials in the photoreceptors of his eyes, each sensitive to different kinds of electromagnetic radiation. A tougher question is how in the world he is seeing these wavelengths in the first place. X-Rays are hard to come by on earth. In medicine, they're created by aiming a high energy electron beam at a target made of tungsten, usually in a vacuum tube. Either the electrons in the beam knock an electron off of an atom of tungsten, causing a higher electron to drop and fill its place, or the nucleus of the tungsten makes the electron beam veer off-target. Either way, the change in energy of the electrons produces a high-energy x-ray photon.
Now, it's been shown that Superman can produce high-intensity lasers with his eyes. In everyday life, that usually involves manipulating photons within a mirrored tube, reflecting them back and forth until they shoot out in sync with each other. The lasers Superman shoots have to be very hot and high-energy. Perhaps he has the ability to produce a chemical reaction energetic enough to cause x-rays to shoot out of his eyes, but they still have to bounce off a surface in order to get back to the photoreceptors in back of his eyes so he can see them.
If the x-rays are energetic enough, they may keep going until they reflect off some surface – x-rays will reflect off mirrors, but only at a shallow angle, so they'd have to reflect many times off many convenient mirrored surfaces – and some come back to him. This would expose whoever he's looking at to not one but two doses of radiation. It's probably better for humanity if he just is extremely sensitive to the few x-rays, and other cosmic rays, that manage to struggle through earth's atmosphere and magnetic field.
By: Moahmed Taha