ОписCooking with radio waves - Chicago Worlds Fair 1933.jpg
English: Demonstration of cooking by radio waves at the 1933 Chicago World's Fair, "Century of Progress", Chicago, Illinois, USA from radio magazine. This was a forerunner of modern microwave ovens which were developed in the 1950s. At Westinghouse Corp's "Powercasting" exhibit of futuristic shortwave technology, sandwiches were cooked by placing them between metal plates of a powerful 10 kW 60 MHz short wavetransmitter, as shown. The magazine article (p. 394) says steaks, potatoes, and vegetables were also cooked in a few minutes. The exhibit also demonstrated wireless power transmission; a 1/4 horsepower motor was run by radio waves over a distance of 30 feet, and audience members could expose their bodies to the radio waves and feel the heat generated. The short wave technology was developed at Westinghouse research laboratories by I. F. Mouromtseff, and the demonstrations were conducted by G. R. Severance and film star Fifi D'Orsay(shown)
This 1933 issue of Short Wave Craft magazine would have the copyright renewed in 1961. Online page scans of the Catalog of Copyright Entries, published by the US Copyright Office can be found here. Search of the Renewals for Periodicals for 1960, 1961, and 1962 show no renewal entries for Short Wave Craft. Therefore the copyright was not renewed and it is in the public domain.
Note that it may still be copyrighted in jurisdictions that do not apply the rule of the shorter term for US works (depending on the date of the author's death), such as Canada (70 years p.m.a.), Mainland China (50 years p.m.a., not Hong Kong or Macao), Germany (70 years p.m.a.), Mexico (100 years p.m.a.), Switzerland (70 years p.m.a.), and other countries with individual treaties.
Actress Fifi D'Orsay assists engineer G. R. Severance in a demonstration of his new method of "cooking by short waves" at the 1933 Chicago World's Fair