1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Reading a book in the infrared

  1. Feb 12, 2010 #1
    If you walked into a cave that led several stories underground, completely cut off by light, would you be able to read a standard text book you'd carried with you using a set of infrared goggles? Along with a spectrometer? After several days? My guesses are no, in all cases, unless the ink print contained something metallic; in which case you might be able to, until it had cooled to the same stable temperature of the pages.

    This is a long-standing argument with friends, when as kids we were playing D&D with an Elf who came across a tome in a pitch-black dungeon. :)
  2. jcsd
  3. Feb 12, 2010 #2
    Maybe the ink would reflect the infrared body-heat radiation differently from the rest of the page?

    Btw, for different types of objects that are in thermal equilibrium, isn't the thermal radiation spectrum still different from material to material?

  4. Feb 13, 2010 #3
    Light amplification goggles typically use wavelengths 900 nm and shorter. There is little emission from "room temperature" objects at these wavelengths. Without a light source such as an infrared LED (which are available on some light amplification devices), you would not see anything. You would need a thermal imager and the ink would need to have a different emissivity than the paper. You might want to warm up the paper maybe by holding your hand on it for better viewing.
  5. Feb 15, 2010 #4
    Thanks - good points.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook