If a metal has a work function of 2 eV, what is the threshold wavelength for the

Practice Questions

Q1
If a metal has a work function of 2 eV, what is the threshold wavelength for the photoelectric effect?
  1. 620 nm
  2. 400 nm
  3. 500 nm
  4. 300 nm

Questions & Step-by-Step Solutions

If a metal has a work function of 2 eV, what is the threshold wavelength for the photoelectric effect?
  • Step 1: Understand the work function (W). It is the minimum energy needed to remove an electron from the metal. In this case, W = 2 eV.
  • Step 2: Know the equation to find the threshold wavelength (λ): λ = hc/W.
  • Step 3: Identify the constants needed for the equation: h (Planck's constant) = 4.14 x 10^-15 eV·s and c (speed of light) = 3 x 10^8 m/s.
  • Step 4: Substitute the values into the equation: λ = (4.14 x 10^-15 eV·s * 3 x 10^8 m/s) / 2 eV.
  • Step 5: Calculate the numerator: 4.14 x 10^-15 * 3 x 10^8 = 1.242 x 10^-6 eV·m.
  • Step 6: Divide the result by the work function: λ = 1.242 x 10^-6 m / 2 = 6.21 x 10^-7 m.
  • Step 7: Convert meters to nanometers: 6.21 x 10^-7 m = 621 nm.
  • Step 8: Conclude that the threshold wavelength for the photoelectric effect is 620 nm.
  • Photoelectric Effect – The phenomenon where electrons are emitted from a material when it absorbs light of sufficient energy.
  • Work Function – The minimum energy required to remove an electron from the surface of a metal.
  • Threshold Wavelength – The maximum wavelength of light that can cause the photoelectric effect, related to the work function.
  • Planck's Equation – The relationship between energy, wavelength, and frequency, given by E = hc/λ.
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