Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

X ray burning lens

  1. May 9, 2014 #1
    I know that High-energy (hard) X-ray light cannot be focused as easily as visible light by using a burning glass. But why is this? If there was x ray light spread over a normal sized lens with the same intensity as sun light why couldn't it focus? would the material needed for say 50cm^2 magnifying glass light focuser object need to be special?
    could very intense radio waves in the same manner be focused over the same area or any other em waves?
    whats special about sunlight?
     
  2. jcsd
  3. May 9, 2014 #2

    UltrafastPED

    User Avatar
    Science Advisor
    Gold Member

    The index of refraction for x-rays in glass is very close to 1; thus you cannot form a converging lens for this case.

    A common technique is to use a crystal that is bent - the x-rays that are diffracted by the crystal structure are "captured" along the selected crystal paths ... and exit where you want them.

    You can also use glancing incidence reflection, but the angles are very low ... both techniques are used in this paper which discusses the theory and experiment:
    https://www.uni-due.de/agbovensiepen/Publikationen/REVSCI99.pdf [Broken]
     
    Last edited by a moderator: May 6, 2017
  4. May 9, 2014 #3

    UltrafastPED

    User Avatar
    Science Advisor
    Gold Member

    Glass is transparent for only part of the electromagnetic spectrum; for ordinary glass it absorbs starting in the UV at one end, and the infrared at the other.

    You need to select the correct materials for part of the spectrum. Even then each wavelength will have a slightly different focal length: http://hyperphysics.phy-astr.gsu.edu/hbase/geoopt/aber2.html
     
  5. May 9, 2014 #4

    sophiecentaur

    User Avatar
    Science Advisor
    Gold Member

    There is not, ifaik, any substance that will behave, for X rays, the same as glass does for light - i.e. have a high enough refractive index without high transmission loss. X ray telescopes use the oblique reflection on the surface of a metal surface. Rays hitting the metal at near normal incidence will penetrate the surface. The surface is part of a paraboloid, way off axis (up on one side of the paraboloid surface). This link shows how an image can be focussed, using several paraboloid surfaces. To get the image focussed correctly, they also incorporate hyperboloid reflectors.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: X ray burning lens
  1. X Rays (Replies: 8)

  2. Spray Coating for X-ray (Replies: 10)

  3. X-ray diffraction (Replies: 1)

Loading...