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What am I doing wrong? photolelectric effect

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    Metal surface is illuminated with light of wavelength 410nm, photoelectrons are emitted with a maximum kinetic energy of 2.1x10-19 joules.

    Calculate the work function of the metal surface.

    Energy of the photon = C/lambda = F
    = 3x10^8 / 410x10-9 = 7.317x10^14 HZ
    energy of photon = HF = 6.63x10-34 * 7.312x10^14 = 4.85x10^-19 joules.

    To work out work function

    HF = workfunction + max KE
    workfunction = HF - max KE
    = 4.85x10-19 - 2.1x10-19 = 2.75x10-19 joules.

    This is wrong? the answer is supposed to be 1.61x10-19 joules so I don't know what I have done wrong, can anyone help?

    Thanks
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    As far as I can see, your answer is correct.
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    Looks right to me too. Are you doing a book question?
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    (Original post by Hazza616)
    Looks right to me too. Are you doing a book question?
    Yep, its the turning points AQA book

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