Black Body Radiation Experiment This page provides the interactive animated visuals needed for the black body radiation experiment. The grating monochromator shown here is an integral part of this experiment and is more fully discussed under the Chapter "Optics". For the present experiment, the more important visuals are the rotation of the grating and the resulting plot at the right of the monochromator. The disagreement between experiment and theory of black body radiation was the impetus for the birth of quantum mechanics. The components shown here are the ones that were needed to perform the experiment. The expression for the spectral radiance, L(lam), in terms of power per steradian per nanometer per meter^2 is the following: R(lam,T)=2*h*c^2/lam^5*dLam/[exp(h*c/(lam*k*T))-1] where h is Planck's constant, c is the speed of light, lam is the wavelength expressed in meters, k is Boltzmann's constant, and dLam is just 10e-9 which is the length of a nanometer expressed in meters. The black body temperature of the Sun is 5780 K and its diameter subtends 0.53 degrees when measured from Earth. If one integrates this R(lam,5780) over wavelength to compute the total solar power falling at the upper atmosphere of Earth, the result will be 1360 Watts per meter squared as was measured by satellite. For more detailed information about the experiment and the birth of quantum theory, click the links below.
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phiG phiB scanAmp T Single Step Scan Grating Wavelength