Physicopoeia

φυσικοποιΐα
THINGS I WISH I'D KNOWN WHEN I STARTED TEACHING PHYSICS

Black Body Curves

This crops up when teaching thermal physics, stars and just sometimes as a random question from younger pupils ('why do objects go red-hot, then orange and yellow, and then white-hot but not green-hot?').

Historically, this bit of Physics was very significant in the transition from classical to quantum physics around the turn of the 20th century (to find out more, search for 'the ultra-Violet catastrophe'). To save you sketching graphs by hand and running the risk of getting them wrong, I've put together an Excel file which plots an emission curve for a black body at any temperature - you can change the temperature and immediately see how the curve changes:

Wien first spotted the pattern shown by the red dashed line in 1893 empirically, but it wasn't until 1900 that Planck was able to convincingly show how this could be predicted theoretically - he was only able to do this by assuming energy was quantized.

Wien's Law curves.xlsx

Also included in the above Excel file is a plot of multiple curves for black bodies of differing temperatures so you can see how things change: