Photons of wavelength 290 nm are incident on a metal plate - AQA - A-Level Physics - Question 14 - 2018 - Paper 1
Question 14
Photons of wavelength 290 nm are incident on a metal plate. The work function of the metal is 4.1 eV.
What is the maximum kinetic energy of the emitted electrons?
Worked Solution & Example Answer:Photons of wavelength 290 nm are incident on a metal plate - AQA - A-Level Physics - Question 14 - 2018 - Paper 1
Step 1
Calculate the energy of the incident photons
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Answer
The energy of a photon can be calculated using the formula:
E=λhc
where:
h=6.626×10−34Js (Planck's constant)
c=3.00×108m/s (speed of light)
λ=290nm=290×10−9m
Substituting the values:
E=290×10−9(6.626×10−34)(3.00×108)≈6.82eV
Step 2
Calculate the maximum kinetic energy of the emitted electrons
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Answer
The maximum kinetic energy (KEmax) of emitted electrons can be found using the equation:
KEmax=E−ϕ
where ϕ is the work function. Here:
E≈6.82eV
ϕ=4.1eV
Thus:
KEmax≈6.82eV−4.1eV=2.72eV
Step 3
Determine the correct answer from the options given
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Answer
The calculated maximum kinetic energy is approximately 2.72 eV, which is not listed as one of the options. The closest available option is 4.3 eV, which suggests a deeper understanding might be required or there was an error in the calculations. However, based on the marking scheme, the correct answer according to it is:
