Bell Telephone Laboratories
April 1952 Radio-Electronics

April 1952 Radio-Electronics [Table of Contents] Wax nostalgic about and learn from the history of early electronics. See articles from Radio-Electronics, published 1930-1988. All copyrights hereby acknowledged.

There is a physical limit to how small of a distance may separate two distinct objects (line, dots, etc.), generally agreed to be about half a wavelength of the color being observed, and be seen with perfect human eye. Applying that rule of thumb to blue light with a wavelength of approximately 4000 Å (400 nm) yields a distance of 200 nm. Accordingly, there is no amount of magnification possible which will allow a healthy human eye to resolve objects closer together than that. Even with perfect optics, magnifications of greater than about 1500x are not able to render greater detail. To resolve smaller distance requires shorter wavelengths, but we cannot see them directly and need a device to transform the detected image into a visible image. That is what an electron microscope does to enable molecule sized particle to be "seen." The SARS-CoV-2 particle has been measured by electron microscopy and found to range between 50 to 140 nm, so it cannot be viewed directly with an optical microscope. Cigarette smoke is about 400 nm in diameter (at the limit of visible light detection) and readily passes through masks work to "protect" against COVID (which is 1/3 the size).

Bell Telephone Laboratories - Electrons Probe the Future

In 1927, Bell Laboratories physicists demonstrated that moving electrons behave like light waves, and thus launched the new science of electron optics.

Now, through the electron beams of the electron microscope and electron diffraction camera, scientists learn crucial details about the properties of metals far beyond the reach of optical microscopes or chemical analysis.

At the Laboratories, electron beams have revealed the minute formations which produce the vigor of the permanent magnets used in telephone ringers and magnetron tubes for radar. The same techniques help show what makes an alloy hard, a cathode emit more electrons and how germanium must be processed to make good Transistors.

This is the kind of research which digs deep inside materials to discover how they can he made better for your telephone system ... and for the many devices which the Laboratories are now developing for national defense.

1 - Electron micrograph of an alloy of aluminum, nickel, cobalt and iron. Magnification 20,000 diameters.

2 - Cooled from high temperature in a magnetic field, the alloy becomes a powerful, permanent magnet. Note changed structure. Black bars reveal formation of precipitate parallel to the applied field. Each bar is a permanent magnet.

3 - A Bell scientist adjusts electron diffraction camera. Electrons are projected on the specimen at glancing angles. They rebound in patterns which tell the arrangement of the atoms ... help show how telephone materials can be improved.

4 - Diffraction pattern of polished germanium reveals minute impurities which would degrade the performance of a Transistor.

Improving telephone service for America provides careers for creative men in scientific and technical fields.

Bell Telephone Laboratories

Posted May 12, 2022