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Question 1
This question is about the photoelectric effect. |
a) | State what is meant by the work function of a metal.
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b) | A photon of frequency 2.00 x 1015 Hz is incident on a zinc plate. The work function of the zinc is 4.33 eV. Calculate the kinetic energy of the emitted photoelectrons.
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c) | The kinetic energy of the photoelectrons emitted varies up to a maximum. Explain why the photoelectrons have a range of kinetic energies.
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d) | The intensity of the incident light is doubled. Explain what effect doubling the intensity of light has on the photoelectrons emitted.
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Question 2
A student is investigating the photoelectric effect using different sources of light and a metal plate. |
a) | State what is meant by the term threshold frequency.
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b) | The work function of the metal plate is 4.33 eV. The metal plate is inside a vacuum photocell which the student connects to a sensitive ammeter. Describe what the student would observe when they illuminate the metal plate with each of the three light sources. The intensity of each light source is the same.
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c) | Light source 3 is used to illuminate the metal plate. The student applies a potential difference across the photocell which reduces the current to zero. Calculate the stopping potential for the metal plate.
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Question 3
A student is investigating the photoelectric effect using a vacuum photocell. The student varies the frequency of the light source and records the current on the microammeter. The student's results are in the table below. |
a) | Calculate the missing value in the table for maximum kinetic energy.
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b) | The student plotted a graph of frequency against maximum kinetic energy. What does the x-intercept represent?
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c) | State what the y-intercept represents.
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d) | State what the gradient of the graph represents.
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e) | The student keeps the frequency of light the same and slowly decreases the intensity of light. Describe what the student would observe on the microammeter.
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Question 4
The diagram below shows the energy levels for hydrogen gas. |
a) | State the name of the energy level labelled - 13.6 eV.
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b) | Calculate the frequency of an incident photon that excites an electron in the ground state to the -1.51 eV energy level.
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c) | Identify the state of an electron in the energy level labelled 0.
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d) | Explain why the energy levels are all negative.
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e) | A photon of energy 12.75 eV is incident on an electron in the ground state causing it to become excited. Draw on all the different photons that could be released as the electron de-excites.
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Question 5
A student is investigating electron diffraction. A beam of electrons is fired at a thin graphite sheet in an evacuated tube. |
a) | The electrons are accelerated through a potential difference of 2,500 V. Calculate the speed of the accelerated electrons.
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b) | Describe what the student will observe on the fluorescent screen.
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c) | The student slowly increases the accelerating voltage from 2,500 V. Describe and explain how the pattern on the fluorescent screen will change.
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Question 6
This question is about the photoelectric effect as evidence for the particle like nature of light. |
a) | State what is meant by the photoelectric effect.
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b) | Explain why wave theory cannot be used to explain the photoelectric effect.
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c) | The metal plate has a work function of 0.9 eV. Light of wavelength 410 nm is incident on the plate. Calculate the maximum speed of the photoelectrons emitted.
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d) | The intensity of the light source is doubled and the frequency of incident light is halved. Describe the effect of these changes on the emitted photoelectrons.
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Question 7
Fluorescent bulbs are filled with mercury vapour at low pressure. |
a) | Describe what happens to electrons in the ground state of the mercury vapour when an potential difference is applied across the fluorescent bulb.
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b) | The mercury vapour emits photons as it de-excites. State which part of the electromagnetic spectrum these photons belong to.
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c) | Describe how the photons emitted by the mercury vapour allow the fluorescent bulb to operate.
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d) | Explain why photons of characteristic frequencies are emitted by the fluorescent coating.
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Question 8
The diagram below shows the energy levels for a sample of hydrogen gas. |
a) | State the name of the energy level labelled -13.6 eV.
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b) | Explain what happens when a photon of energy 12.6 eV is incident on a ground state electron.
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c) | Another photon is incident on an electron in the ground state causing it to become excited to the -0.54 eV energy level. Calculate the frequency of the incident photon.
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d) | The electron de-excites from the -0.54 eV energy level. Calculate the longest possible wavelength of photon emitted.
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