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: Designing an experiment to demonstrate Planck's Law

  1. Apr 10, 2015 #1
    For my undergraduate physics lab, we are asked to spend 3 weeks (3 3-hour sessions + any time during the week if I need extra time) doing an experiment of our own choosing. The physics department will provide any experimental tools needed within reason.

    I have been considering using this time to measure the intensity vs. wavelength of the light emitted from a tungsten filament at different temperatures. I would do this by focusing the emitted light through a lens then separating the wavelengths with a prism and finally detecting the intensity by wavelength with a spectrometer. I would then plot my data against the graph of Planck's law and determine how closely the two fit.

    Do you think that this would be a good experiment for this lab? Also do you think there are any other tools I would need? Maybe a voltage amplifier to get the Tungsten to a higher temperature? Can you think of any problems I would have?

    Thanks for your help!
  2. jcsd
  3. Apr 10, 2015 #2


    User Avatar
    Gold Member

  4. Apr 10, 2015 #3
    Is there a way that I could use a tungsten filament without the bulb/glass to avoid the infrared light being absorbed without the tungsten catching fire? Or is there another material that I could use to get a nice full Planck curve?
  5. Apr 11, 2015 #4


    User Avatar
    Gold Member

    I think a tungsten filament will work in air up to dull red, or evn organge with short.
    If you smash the glass envelope of a Tungsten bulb. I think the filament will operate in air for some time if you keep it to red or orange. You need to experiment. May I mention that I have found that glass lenses etc tend to warm up during an experiment, and then radiate IR.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted