|MadSci Network: Physics|
Hello Justin, Indeed, your teacher was correct. There really is no "known" form of matter that will block all "light". The ability of materials to block (absorb) photons of light is mostly a function of the density of the material. As the wavelength of photons decrease ( the frequency increases ), their ability to pass through materials increases, but, with thick enough material, all of the photons will eventually be absorbed. This process is known as the 'photoelectric effect'. You can see this effect with a flashlight and some paper ( your physics textbook would even work). In a dark room, put the flashlight up against a few pages of paper. You can see the some of the light coming through the pages. Add more pages and you see less light. Find a brighter source of light and more photons will pass through a given number of pages. Even with very dense material like lead or tungsten, higher energy forms of electromagnetic energy ( like X-rays ) will pass through some thickness of the material. If you make the material thick enough, it will block all of the X-Rays. Check out this web link for a more in-depth description. http://acept .la.asu.edu/PiN/rdg/visnxray/visnxray.shtml
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