1. What is the longest-wavelength EM radiation that can eject a photoelectron from silver, given that the binding energy is 4.73 eV? Is this

Question

1. What is the longest-wavelength EM radiation that can eject a photoelectron from silver, given that the binding energy is 4.73 eV? Is this in the visible range?
2. Find the longest-wavelength photon that can eject an electron from potassium, given that the binding energy is 2.24 eV. Is this visible EM radiation?

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Gerda 1 month 2021-08-01T09:15:13+00:00 1 Answers 45 views 0

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    2021-08-01T09:16:46+00:00

    Answer:

    1. λ = 2.626 x 10⁻⁷ m = 262.6 nm

    This wavelength is not in visible range. It lies in Ultra Violet Region.

    2. λ = 5.546 x 10⁻⁷ m = 554.6 nm

    This wavelength is in visible range.

    Explanation:

    The binding energy of in photoelectric effect is also known as work function. The formula for this is given as follows:

    Binding Energy = Work Function = hc/λ

    λ = hc/Work Function   ————— equation (1)

    where,

    h = Plank’s Constant = 6.626 x 10⁻³⁴ J.s

    c = speed of light = 3 x 10⁸ m/s

    λ = longest wavelength capable of ejecting electron = ?

    (1)

    Here,

    Work Function = (4.73 eV)(1.6 x 10⁻¹⁹ J/1 eV) = 7.568 x 10⁻¹⁹ J

    Therefore,

    λ = (6.626 x 10⁻³⁴ J.s)(3 x 10⁸ m/s)/(7.568 x 10⁻¹⁹ J)

    λ = 2.626 x 10⁻⁷ m = 262.6 nm

    This wavelength is not in visible range. It lies in Ultra Violet Region.

    (2)

    Here,

    Work Function = (2.24 eV)(1.6 x 10⁻¹⁹ J/1 eV) = 3.584 x 10⁻¹⁹ J

    Therefore,

    λ = (6.626 x 10⁻³⁴ J.s)(3 x 10⁸ m/s)/(3.584 x 10⁻¹⁹ J)

    λ = 5.546 x 10⁻⁷ m = 554.6 nm

    This wavelength is in visible range.

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