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Expert-verifiedQuestion: What is the wavelength of EM radiation that ejects \(2.00\,{\rm{eV}}\) electrons from calcium metal, given that the binding energy is \(2.71\,{\rm{eV}}\)? What type of EM radiation is this?
Wavelength of the radiation is \(263 \times {10^{ - 9}}\,{\rm{m}}\)
Type of EM radiation is Ultra violet.
The kinetic energy of the electron is given by
\(K{E_e} = hf - BE\) ...(1)
Here \(K{E_e}\) is the kinetic energy, \(h\) is the plank constant, \(f\]) is the frequency of the EM radiation and \(BE\) is the binding energy.
Now we know that the wavelength of EM radiation is given by
\(\lambda = \frac{c}{f}\) ...(2)
Where \(c\) is the speed of light.
So equation becomes,
\(K{E_e} = \frac{{hc}}{\lambda } - BE\) ...(3)
The total energy of the photon is
\(\begin{array}{c}E = (2.00\,{\rm{eV}}) + (2.71\,{\rm{eV}})\\ = 4.71\,{\rm{eV}}\end{array}\)
We also know that: Planks constant \(h = 4.13 \times {10^{ - 15}}\,{\rm{eV}}{\rm{.s}}\)
Speed of light \(c = 3 \times {10^8}\,{\rm{m/s}}\)
The wavelength of the radiation is expressed as,
\(\lambda = \frac{{hc}}{E}\)
Substitute all the value in the above equation
\(\begin{array}{c}\lambda = \frac{{\left( {4.13 \times {{10}^{ - 15}}\,{\rm{eV}}{\rm{.s}}} \right)\left( {3 \times {{10}^8}\,{\rm{m/s}}} \right)}}{{(4.71\,{\rm{eV}})}}\\ = 263 \times {10^{ - 9}}\,{\rm{m}}\end{array}\)
Therefore, the wavelength of the radiation is \(263 \times {10^{ - 9}}\,{\rm{m}}\)
Hence, the wavelength of the EM radiation is \(263\,{\rm{nm,}}\) the radiation type is ultra violet.
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