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March 24, 2017

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Electrons are ejected from a metallic surface with speeds ranging up to 4.50x10^5 m/s when light with a wavelength of 615nm is used. (a) What is the work function of the metal? (b) What is the cutoff frequency for this surface?

  • Physics - ,

    Einstein's photoelectric equation:
    ε =W + KE,
    h•c/λ = W +m•v²/2,
    W = h•c/λ - m•v²/2 =
    = 6.63•10^-34•3•10^8/615•10^-9 - 9.1•10^-31•(4.5•10^5)/2 =
    = 2.3•10^-19 J = 1.44 eV.
    W = h•f,
    f = W/h = 2.3•10^-19/6.63•10^-34 = 3.48•10^14 Hz.

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