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Question
Using values from Table 7.1, how many DNA molecules could be broken by the energy carried by a single electron in the beam of an old-fashioned TV tube? (These electrons were not dangerous in themselves, but they did create dangerous x rays. Later model tube TVs had shielding that absorbed x rays before they escaped and exposed viewers.)
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<b>Table 7.1</b> Energy of various objects and phenomena
Table 7.1 Energy of various objects and phenomena
Question by OpenStax is licensed under CC BY 4.0.
Final Answer
40000 DNA molecules broken per electron
Solution Video

OpenStax College Physics Solution, Chapter 7, Problem 26 (Problems & Exercises) (0:42)

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Video Transcript

This is College Physics Answers with Shaun Dychko. One electron in the cathode ray tube in an old fashioned TV has 4.0 times 10 to the minus 15 joules of energy and the energy it takes to break one strand of DNA is 10 to the minus 19 joules. So the number of DNA molecules broken per single electron is gonna be this number of joules in the electron multiplied by 1 DNA broken for every 10 to the minus 19 joules. And the joule units will cancel and we'll have the number of DNA broken per electron and that works out to 40,000 DNA would be broken by one electron from the TV.