DescriptionUS Patent 755840-Jagadish Chandra Bose-Detector for electrical disturbances fig 1-3.png
English: A galena semiconductor crystal detector for microwaves invented by Indian physicist Jagadish Chandra Bose during his landmark millimeter wave optics experiments 1894-1900. It consists of a tiny crystal of the semiconducting mineral galena (lead sulfide, PbS) (4) with a metal point (5) making electrical contact with it, at the focus of a lens (13) which focuses microwaves on it. A battery (18) passes direct current through the contact and a galvanometer(19) measures the current. When microwaves strike the crystal they reduce the resistivity of the contact, and the galvanometer registers an increase in current. The pressure of the point can be adjusted with a thumbscrew (7). Bose used it to detect microwaves in the frequency range from 12 to 60 GHz generated by a spark transmitter in the first historic experiments with millimeter waves, in which he duplicated classical optics experiments, demonstrating refraction, diffraction, polarization, and standing waves, proving that microwaves are electromagnetic waves predicted by James Clerk Maxwell in 1873. The detector is deliberately built to resemble and function similarly to a human eye; due to Maxwell's theory, physicists of this era regarded radio waves as "invisible light". Bose called his detector an artificial retina. This was the first crystal detector (semiconductor diode) and is often considered the first patent on a semiconductor device.
Alterations to image: cropped out surrounding heading text and signatures.
In specific cases, patent applicants and holders may claim copyright in portions of those documents. In those specific cases, applicants are required to identify the portions that are protected under copyright, and are additionally required to state the following within the body of the application and patent (see 37 CFR 1.71(d) & (e) and 37 CFR 1.84(s), and MPEP § 608.01(e) & (w) and MPEP § 1512):
A portion of the disclosure of this patent document contains material which is subject to (copyright or mask work) protection. The (copyright or mask work) owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in the Patent and Trademark Office patent file or records, but otherwise reserves all (copyright or mask work) rights whatsoever.
The original patent should be checked for the presence of such language before an assumption is made that the contents are in the public domain. (This template can be replaced by {{PD-US-patent-no notice}} in such cases.)
This media file is in the public domain in the United States. This applies to U.S. works where the copyright has expired, often because its first publication occurred prior to January 1, 1929, and if not then due to lack of notice or renewal. See this page for further explanation.
United States
This image might not be in the public domain outside of the United States; this especially applies in the countries and areas that do not apply the rule of the shorter term for US works, such as Canada, Mainland China (not Hong Kong or Macao), Germany, Mexico, and Switzerland. The creator and year of publication are essential information and must be provided. See Wikipedia:Public domain and Wikipedia:Copyrights for more details.
Captions
Diagram of a galena crystal radio wave detector invented by Jagadish Chandra Bose