Heat and Thermodynamics

12.8 The Wavelength-Temperature Displacement Law

For the sake of convenience of proof, we perform an imaginary experiment. Suggested by Larmor to simplify the calculation, we take an enclosure of the shape of a sphere of radius r (Fig.12.9). It has got perfectly reflecting interior walls consisting of small segments of perfect mirror oriented at random so as to obtain diffuse reflection and is impervious to heat and is capable of uniform adiabatic expansion in the radial direction. Since the volume of the sphere is proportional to the cube of its radius, Eq. 12.34 takes the following form

 

 

Fig. 12.9 Change in wavelength on reflections