WorksheetsPre-U Review: Quantum
Total questions: 39
Worksheet time: 39mins
Which of the following best describes a photon?
an electron emitted from a metal surface by the action of light
a unit of energy
a positively-charged atomic particle
a quantum of electromagnetic radiation
Which of the following graphs shows the variation of the energy E of a photon of light with its wavelength λ?
The given list shows three energies: Which sequence has the energies in increasing order of magnitude?
1 2 3
1 3 2
2 1 3
2 3 1
Which of the following has the greatest energy content?
102 photons of wavelength 1 pm (𝛾-rays)
105 photons of wavelength 2 nm (X-rays)
106 photons of wavelength 5 µm (infra-red radiation)
108 photons of wavelength 600 nm (yellow light)
After travelling through a vacuum, a photon of light enters a block of glass.
Which of the following correctly describes the changes to the energy of the photon?
increases because its associated wavelength decreases
decreases because the speed of the radiation decreases
stays the same because the speed of the radiation and the associated wavelength do no change
stays the same because the frequency of the radiation does not change
Which phenomenon cannot be explained by the wave theory?
diffraction
interference
photoelectric emission
polarisation
Which of the following about photoelectric emissions is true?
No emission of electrons occurs for very low intensity illumination
For a given metal there is a minimum frequency of radiation below which no emission occurs
The velocity of the emitted electrons is proportional to the intensity of the incident radiation
The number of electrons emitted per second is independent of the intensity of the incident radiation
Electrons are emitted when a monochromatic beam of red light falls on one electrode of a photo-cell. If the light beam is replaced by a monochromatic blue beam of the same power, which of the following quantities would decrease?
The maximum kinetic energy of the electrons emitted
The number of photons striking the metal per unit time
The energy of each photon striking the electrode
The work function of the metal
Photoelectrons may be emitted when electromagnetic radiation of frequency f falls on a particular metal surface. The given graph shows how the maximum kinetic energy E of these electrons varies with f. The experiment is then repeated using another metal of greater work function energy.
Which of the following graphs will be obtained?
In an experiment on the photoelectric effect, light of various frequencies were used to illuminate metals X and Y, and the potential difference V required to stop the photoelectrons is measured.
The work function of Y is known to be greater than that of X.
Which of the following graphs correctly illustrates the expected results?
An evacuated photocell with a pure metal cathode is used in a photoemission experiment. The potential difference y required to stop the photoelectrons is measured for various frequency x.
Which of the following graphs best represents the variation of y with x?
The cathode of a photocell is illuminated by light quanta of energy 3.5 x 10-19 J each. By applying a stopping potential of 0.25 V, the current through the cell is just reduced to zero.
Which of the following is the work function energy of the cathode?
2.9 x 10-19 J
3.1 x 10-19 J
3.5 x 10-19 J
3.9 x 10-19 J
In an experiment on the photoelectric effect, the wavelength of the incident light is increased. Which of the following is the effect of this change on the kinetic energy of the emitted electrons?
The average kinetic energy decreases
The average kinetic energy increases
The maximum kinetic energy increases
The minimum kinetic energy decreases
A photocell, connected to a supply, is exposed to monochromatic radiation. A current is found to flow only when the potential difference across the cell is less than 1.6 V.
Which of the following is the maximum energy of the photoelectrons?
1.0 x 10-19 J
2.6 x 10-19 J
4.8 x 10-11 J
1.6 J
The maximum kinetic energy E(k) of emitted electrons is measured in photoemission experiments using light of a particular wavelength.
Which of the following graphs correctly shows how E(k) varies with the intensity I of the light?
In experiments on the photoelectric effect, the potential difference V required to stop the photoelectrons is measured for various frequency f. The variation of V with f is as shown.
What is the maximum kinetic energy of the electrons emitted at frequency f₁?
hf₁
V₁ / (f₁ - f₀)
h (f₁ - f₀)
V₁
Electrons are emitted when monochromatic ultra-violet radiation falls on a clean metal in a vacuum. If the intensity of the radiation is doubled, what could also be doubled?
the maximum speed of the electrons
the maximum kinetic energy of the electrons
the rate of emission of the electrons
the threshold frequency of the metal surfaces
Photoelectrons are emitted from a zinc plate when it is illuminated by an ultra-violet radiation. The maximum kinetic energy of the photoelectrons is E(k) and the number of photoelectrons emitted per second is n.
If the plate is illuminated by a more intense source of the same frequency, how will E(k) and n be affected?
A
B
C
D
The photoelectric effect refers to the phenomenon that electrons may be ejected from a metal surface when light falls on the surface. Which of the following is correct?
Electrons are ejected only if the wavelength of the incident light is greater than some minimum value.
The maximum energy of the electrons is independent of the intensity of the incident light.
The maximum energy of the electrons is independent of the type of metal
The waves associated with the ejected electrons have the same wavelength as the incident light
In a photoelectric emission experiment, light from various monochromatic sources, of different frequencies and variable intensities, were used to illuminate various metals.
For a given metal, frequency and intensity, the emitted electrons were found to have a spread of kinetic energies up to a maximum value.
Which of the following affects this maximum kinetic energy?
A
B
C
D
In experiments on the photoelectric effect, the quantities investigated were threshold frequency f₀, frequency of incident light f, light intensity P, photocurrent I, and maximum kinetic energy of photoelectrons T_max.
When plotted as a graph of y against x, two of these quantities give a straight line through the origin. What are these quantities?
A
B
C
D
A monochromatic light falls on a metal surface in an evacuated enclosure. Electrons emitted from the metal plate are collected by an adjacent electrode. For a given light intensity, the given graph shows how the photocurrent I varies with the potential difference V between the electrodes.
The intensity of the light is then doubled.
Which graph best shows the new relation between I and V?
[The graph representing the original experiment is shown as a dashed line.]
Photoelectrons are emitted from a given metal surface when it is illuminated by two beams, P and Q, of light of the same frequency. P produces a photoelectric current with four times the magnitude that Q produces.
What is the value of the ratio (wave amplitude of beam P) / (wave amplitude of beam Q) ?
1/4
1/2
2
4
Photoelectrons are emitted when a beam of monochromatic radiation illuminates a metal X. Which of the following will double the rate of photoelectron emission?
a beam of double the intensity is used
radiation of double the frequency is used
radiation of double the wavelength is used
the thermodynamic temperature of the metal is doubled
Which experimental result suggested the wave nature of electrons?
line spectra of atoms
the production of X-rays
the photoelectric effect
electron diffraction by a crystalline material
An electron of mass m_e is moving with a speed of 0.02 c, where c is the speed of light in space.
Which expression gives the de Broglie wavelength of the electron?
A beam of monochromatic light has its intensity doubled.
What is the corresponding change, if any, in the momentum of each photon of the radiation?
increased fourfold
double
the same
halved
A particle of mass m has kinetic energy E.
Which of the following gives the de Broglie wavelength of the particle?
h √(2mE)
√(2mE) / h
h / √(mE)
h / √(2mE)
When a beam of light of wavelength λ is incident normally on a plane mirror, it is reflected totally. The intensity of the light corresponds to a rate of n photons per second. In the expressions below, h is the Planck constant. What is the force exerted on the mirror by the beam of light?
n h λ
n h / λ
2 n h λ
2 n h / λ
According to de Broglie, an electron of momentum p is associated with a wave of wavelength λ. Which graph correctly shows how λ varies with p?
The particles listed below have the same de Broglie wavelength.
Which one must have the lowest velocity?
proton
alpha particle
deuterium nucleus
electron
Which of the following explains why electron microscopes are able to distinguish smaller objects than optical microscopes?
electrons are smaller than visible quanta
the electrons travel much faster than light
there is no chromatic aberration with electrons
the electron wavelength is much shorter than that of visible light
Which phenomenon provides direct evidence for discrete energy levels in atoms?
the spectrum of a tungsten filament lamp
the spectrum of a sodium discharge lamp
the photoelectric effect
the emission of β particles by radioactive atoms
Which observation directly demonstrated the existence of discrete energy levels within atoms?
atoms can emit line spectra
photoelectrons are only emitted for wavelengths greater than a critical wavelength
some alpha particles are reflected back through very large angles by atoms in a solid
X-rays with frequencies up to a certain maximum are emitted by a target
Five phenomena associated with photons and/or charged particles are as shown:
Which phenomena directly demonstrated the existence of discrete electronic energy levels within atoms?
1 and 5 only
2 and 3 only
3 and 4 only
2, 3, 4 and 5 only
The five energy levels of an atom are shown in the scale drawing. The directed lines represent five possible transitions between the energy levels.
A photon of definite energy and frequency is produced by each transition.
Which of the spectra best corresponds to the transitions?
A
B
C
D
The average diameter of an air sac in a typical human lung is about 0.25 mm. An oxygen molecule of mass 5.30 x 10-26 kg is trapped within such a sac. Which of the following is the order of magnitude of the minimum uncertainty in its velocity?
10-6 ms-1
10-8 ms-1
10-10 ms-1
10-12 ms-1
The momentum of a proton is measured with an uncertainty of 1.00 %. Given that it has a kinetic energy of 1.00 MeV, which of the following is the minimum uncertainty in its position.
9.08 x 10-13 m
2.28 x 10-13 m
9.08 x 10-14 m
5.64 x 10-14 m
There is an assertion that "the kinetic energy of a harmonic oscillator is not zero at absolute zero temperature". Which of the following could explain this assertion?
The photoelectric effect
The particulate nature of the oscillator
The Heisenberg uncertainty principle
The quantum tunneling effect
