Instruments University of Toronto Scientific Instruments Collection

Preservation of scientific instruments www.utsic.org

Kirchoff 1824 - 1887 D-line... Kirchoffs theorem (1859). Formulating an idea for black body radiation

Ev / Av = J(v, T)...didn't know what the form of J was A black body has Av = 1 challenged physicists to find the function of J To find J, needed to define a black body and other things

Stefan Boltzmann developed the J function further, found the Stefan Boltzmann law, which defines the

energy for a range of frequency Weins displacement law Wein guessed a function for rho(v, T)...which was a part of the Stefan-Boltzmann law didnt work for measurements in the far infrared light region Einstein later uses this guess to develop his heuristic viewpoint

Planck Planck guessed another formula for rho(v, T) (1900) worked for a lot more experimental results for oscillators in emf, joint equilibrium condition where the frequency distribution, rho, is

balanced with the energy in the oscillators decided to work backwards to find U (energy of oscillator) found the entropy of the linear oscillators, got back to the Planck Distribution (by

counting discrete energy quanta) Einstein started by pointing out problems with Plancks derivation integrating plancks distribution over all frequencies theoretically gives you

infinity...doesnt make sense heuristically - rule of thumb approach...which is why it had a hard time getting accepted

as a theory inphysics because he only used Weins region of the distribution and a classical ideal gas how serious do we take this heuristic viewpoint is a strong facet of the paper

uses the thermodynamics of an ideal gas in a subvolume to develop the behaviour of radiation in a subvolume

monochromatic radiation of low density...behaves thermodynamically as if consisted of

mutually independent energy quanta of magnitude [=hv] proves stokes rule using quantum analysis and conservation of energy and then photoelectric effect

Photoelectric effect Hertz, spark experiments cathode rays are disturbances in the aether