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Light in a Photo-tube

  1. Jun 13, 2004 #1
    I am having trouble answering this question.

    When violet light is beamed onto a negative electrode in a photo-tube, a current begins to flow in the tube. Consider the following forms of electric radiation : Blue Light; infrared radiation; ultraviolet radiation. Which of these must also cause a current to flow in the tube, provided all other conditions remain the same?

    I was stuck between Blue light and all three. I don't know which it is.
  2. jcsd
  3. Jun 14, 2004 #2

    Doc Al

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    Staff: Mentor

    Arrange the radiations in the order of increasing energy per photon (increasing frequency). Which, if any, has at least as much energy as the violet light?