File:Refraction of Hertzian waves by paraffin prism.png
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Summary
| Description |
English: Early microwave spectroscopy experiment by John Ambrose Fleming in 1897, repeating historic experiment done by Heinrich Hertz around 1888. A spark gap transmitter A powered by an induction coil I generates a beam of microwave radio waves, which is refracted through an angle by the solid paraffin prism P and detected by the coherer receiver B. This demonstrates that radio waves experience refraction like light waves. By measuring the angle at which the beam is bent the refractive index of paraffin for microwaves can be determined.
The circuit is described and diagrammed on p. 410, fig. 7 of the source. The transmitter A consists of two collinear brass rods about 4 in. long with brass balls on their adjacent ends 1 mm apart to make a spark gap, inside an open zinc box that serves as a horn antenna. When excited by a spark created by high voltage from the coil, the rods function as a half-wave dipole antenna. Although this should mean the antenna should generate radio waves with a wavelength of 16 inches (40.6 cm), the text says the antenna radiates waves with a wavelength of 8 in. (20.3 cm) which would have a frequency of about 1.48 GHz. The waves are detected by a coherer in a similar zinc horn antenna B, consisting of a glass tube with two electrodes with nickel metal filings filling the space between them. The coherer is attached by wires C to a DC circuit with a battery and electric bell (not shown). When exposed to radio waves, the coherer conducts electricity from the battery, ringing the bell. To return the coherer to a nonconductive state, it is given a sharp tap. |
| Date | |
| Source | Downloaded May 5, 2013 from John Ambrose Fleming (1916) The Principles of Electric Wave Telegraphy and Telephony, 3rd Ed., Longmans, Green, & Co., London, p. 413, fig. 9 on Google Books |
| Author | John Ambrose Fleming |
| Permission (Reusing this file) |
Public domain - Published in US prior to 1923 |
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| Date/Time | Thumbnail | Dimensions | User | Comment | |
|---|---|---|---|---|---|
| current | 04:37, 20 May 2013 | | 2,548 × 1,288 (25 KB) | Chetvorno | {{Information |Description ={{en|1=Early microwave spectroscopy experiment by John Ambrose Fleming A en:spark gap transmitter ''(right)'' generates en:microwave en:radio waves, which are refracted through an angle by the prism mad... |
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