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The threshold wavelength for the photoelectric effect for silver is 262 nm. (a) Determine the work function for silver. (b) What is the maximum kinetic energy of an electron emitted from silver if the incident light has a wavelength of 222 nm

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Answer with Explanation:

We are given that

Threshold wavelength,[tex]\lambda_0=262 nm=262\times 10^{-9} m[/tex]

[tex]1 nm=10^{-9} m[/tex]

a.Work function,[tex]w_0=\frac{hc}{\lambda_0}[/tex]

Where [tex]h=6.626\times 10^{-34}[/tex]

[tex]c=3\times 10^8 m/s[/tex]

Using the formula

[tex]w_0=\frac{6.626\times 10^{-34}\times 3\times 10^8}{262\times 10^{-9}}[/tex]

[tex]w_0=7.59\times 10^{-19} J[/tex]

b.Wavelength,[tex]\lambda=222nm=222\times 10^{-9} m[/tex]

[tex]K.E=\frac{hc}{\lambda}-7.59\times 10^{-19}[/tex]

[tex]K.E=\frac{6.626\times 10^{-34}\times 3\times 10^8}{222\times 10^{-9}}-7.59\times 10^{-19}[/tex]

[tex]K.E=8.95\times 10^{-19}-7.59\times 10^{-19}=1.36\times 10^{-19} J[/tex]

Hence, the maximum kinetic energy of an electron emitted=[tex]1.36\times 10^{-19} J[/tex]

Lanuel

a. The work function for silver is equal to 4.73 eV.

b. The maximum kinetic energy of an electron emitted from silver is [tex]1.38 \times 10^{-19}\;Joules[/tex].

Given the following data:

  • Threshold wavelength of silver = 262 nm
  • Wavelength of light = 222 nm

a. To find the work function for silver, we would use Einstein's equation for photon energy:

Mathematically, Einstein's equation for photon energy is given by the formula:

[tex]E = hf = h\frac{v}{\lambda}[/tex]

Where:

  • E is the maximum kinetic energy.
  • h is Planck constant.
  • f is photon frequency.
  • [tex]\lambda[/tex] is the wavelength.
  • v is the speed of light.

When the maximum kinetic energy of an electron is equal to zero (0), the work function of the electron is given by:

[tex]\phi = \frac{hv}{\lambda_t}[/tex]

h = [tex]6.626 \times 10^{-34}\;J.s = 4.136 \times 10^{-15} \;eV.s[/tex]

Substituting the given parameters into the formula, we have;

[tex]\phi = \frac{4.136 \times 10^{-15} \times 3.0 \times 10^{8}}{262}\\\\\phi = \frac{1240}{262}[/tex]

Work function, [tex]\phi[/tex] = 4.73 eV

b. To find the maximum kinetic energy of an electron emitted from silver, if the incident light has a wavelength of 222 nm:

[tex]K.E_{max} = \frac{hc}{\lambda} - \phi\\\\K.E_{max} = \frac{4.136 \times 10^{-15} \times 3.0 \times 10^{8}}{222} - 4.73\\\\K.E_{max} = \frac{1240}{222} - 4.73\\\\K.E_{max} = 5.59 - 4.73\\\\K.E_{max} = 0.86\;eV[/tex]

[tex]1 \;eV = 1.602 \times 10^{-19}\;J[/tex]

[tex]0.86 \;eV = 0.86 \times1.602 \times 10^{-19}\;J\\\\0.86 \;eV = 1.38 \times 10^{-19}\;Joules[/tex]

Maximum kinetic energy = [tex]1.38 \times 10^{-19}\;Joules[/tex]

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