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!

Homework Help: Spectrum of 6V 15W Tungsten Microscope Lamp

  1. Feb 27, 2012 #1
    Dear All

    I am trying to measure the spectrum of an incandesant 6V 15W tungsten microscope lamp. I have a reasonably old scanning monochromator (diffraction grating based) coupled to a fibre optic cable and it has given me the spectrum below.

    http://dl.dropbox.com/u/15546679/silver_lamp_forum.png [Broken]

    I think it maybe broken as I am having a hard time believing that it gives virtual no output at 900nm. Surely all standard tungsten bulbs give out significant radiation at 900nm-1000nm (NIR)? I know it depends on the temperature of the filament and hence the colour temperature, but from most graphs I have seen of tungsten bulbs (2000-3300K), they have spectrums that extend significantly into the 900nm+ NIR region. Unfortunately, I can not find the colour temperature of the bulb, but it is definitely a yellow light so probably in the region 2000-3000K.

    Does anyone else think that the spectrum maybe incorrect and that the monochromator may be broken or be attenuating the spectrum significantly in the 700-900nm region?

    Many thanks

    Last edited by a moderator: May 5, 2017
  2. jcsd
  3. Mar 1, 2012 #2
    It certainly looks attenuated - especially above the 790 nm mark. Have you tried pointing the spectrometer at the sun to see if those wavelengths show up? Unless it's broken, the only other thing I can think of is the possibility that your microscope has one of those infrared filters on it to keep the lamp from heating the sample as much as it otherwise would.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook