Question:

Help with the Photo-Electric effect

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I have a question about the Photo-Electric effect. I was given a table of data, with six values for wavelengths, and six values for stopping potential, and was asked to create a graph to find the work function, threshold freq and Planck's constant which I have done. The next question asks if the intensity of the incident radiation was doubled for all of the wavelengths, and the metal employed to produce photoelectrons had a lower work function (with all other parameters unchanged) how would the data in the table change?

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  1. If you double the intensity, you will get twice as many electrons, but each of them will have the same stopping potential as before.

    If the metal has a lower work function, the threshold frequency will be lower but the slope of your line will be the same.

    Reasoning: if you double the intensity, you double the number of photons but not the energy of each one.  If you change the work function, you simply change the amount of photon energy required simply to remove the electron from the solid.


  2. photon energy  (hf)= hc/wavelengh also drawn like an upside y symbol

    you are given the wavelength, note use correct decimals eg micro ^-6

    h= plancks constant 6.62x 10^-34

    c= 3x10^8 speed of light.

    you then should get a value for hf

    you then multiply it by the value of an electron volt (ev) 1.6x10^-19. To convert it to enery j.  you could write the value follwed by ev instead of converting.

    a photon is used to promote electrons from one orbital in a atom to a higher orbital. for example  a silicon atom may need a enery  increase from -3.4 to -1.4 ev meaning the wavelength would have to give of value of 2 ev or higher.

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