Cathode-Ray Tube Day

The cathode-ray tube, originally known as the kinescope, was patented on today's date in 1938 by Vladimir Zworykin, a Russian immigrant. Cathode-Ray Tube Day commemorates this event. A cathode-ray tube is a vacuum tube made from a large glass envelope that has one or more electron guns and a phosphorescent screen that's used to display images. The images are created when electron beams are modulated, accelerated, and deflected onto a screen. The images may represent pictures on computer monitors and television sets, electrical waveforms on oscilloscopes, radar targets, and more.

Cathodes are negatively charged electrodes. Cathode rays were discovered in 1869 in early Crookes tubes. The earliest prototype of the cathode-ray tube was invented by German physicist Ferdinand Braun in 1897 and is known as the Braun tube. The first televisions to use the cathode-ray tube were made in the 1920s. In 1925, a television was made that received images with a 40-line resolution; by 1927, the lines had increased to 100. The first commercially available television sets with cathode-ray tubes were manufactured in Germany in 1934. RCA received a trademark for the term cathode-ray tube in 1932, and it was released to the public domain in 1950. By the late 2000s, cathode-ray tubes had largely been replaced by "flat panel" display technologies like LCD, OLED display, and plasma display. But for the great significance they played in the twentieth century, we celebrate them today with Cathode-Ray Tube Day.

How to Observe Cathode-Ray Tube Day

A few ways you could celebrate the day include:

• Use something that has cathode-ray tubes, like an older television or computer monitor.
• Learn more about cathode-ray tubes.
• Build a cathode-ray tube.

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