Abstract
The transient solution of the thermoelastic problem of an instantaneous point source of heat on the surface of a semi-infinite solid is derived by a somewhat heuristic procedure. This solution is adapted to the case of a very thin surface film such as an aluminum reflecting film. A number of approximations are incorporated so that the surface deflection becomes inversely proportional to the product of the radial distance from the point source and the third power of the time. The proportionality constant is a thermoelastic coefficient depending on the thermal, elastic, and emissive properties of the mirror. It is estimated that nearly instantaneous point sources of the order of milliwatts are to be expected and that they result in deflections of the order of seconds of arc for aluminum and quartz. On the basis of this analysis, metal is thermoelastically at least as good as quartz for a mirror material. Pyrex is significantly inferior to both. These results essentially agree with Couder’s.
© 1965 Optical Society of America
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