This month's Challenge Question: Specs & Techs from GlobalSpec:
You are watching TV on an old television set with a cathode ray tube. It’s well-known that TV CRT’s produce x-rays as well as images. To measure the radiation dose coming from the TV set, where should you point the x-ray detector?
And the answer is:
When electrons strike the CRT they stop and produce x-rays, but they are always surrounded by an electric field (see first image below) even when they move. If an electron is brought to a sudden stop, its electric field will not completely stop or disappear. The part of the field near the electron will stop first, but the part of the field “behind” the electron does not yet know about the stop, so it continues moving toward the CRT. At the point of contact with the CRT, a “kink” or “twist” is produced in the electric field (see second image), forcing the x-rays to move sideways at an angle of 90 degrees with respect to the direction of the electron beam. There, if you want to measure the maximum available radiation, align your detector with the surface of the TV set.

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