The Selective Reflection of Heat Waves by Linear Resonators

Vacuum-thermocouple.---The construction of a vacuum-thermocouple of high sensitivity and quick action for measuring heat radiation is described.Isolation of Long Heat Waves.---A method is given for isolating radiation of great purity and having a mean wave-length of 96 {μ}. This radiation is obtained by combining a quartz lens focal isolation apparatus with reflecting surfaces of potassium iodide.The Reflection of Radiation by Linear Electric Resonators of Microscopic Dimensions.---Resonators were ruled from films of silver chemically deposited on glass plates. The reflecting power of such resonators was measured for the 96 {μ} waves. Square resonators, the length of whose sides are small compared with the wave-length reflect little more than bare glass, provided the resonators are separated sufficiently to prevent conduction between adjacent edges. Resonators of equal width and separated by a distance of approximately one half of a wave-length were found to produce a maximum of reflection when their length was equal to 0.3 of the wave-length. The metal strips, although microscopic in size, thus show electrical resonance when stimulated by long heat waves. The results are in every way comparable with those that have been obtained with the longer electric waves.