IB PHYSICS Topic 13 Quantum Physics Test Name:
1. The nucleus
30
Si.
14
A.
B.
C.
D.
30
P
15
6. Which of the following best shows how photon
energy E varies with the wavelength λ of the light?
undergoes radioactive decay to
The particles emitted in the decay are
a positron and an antineutrino.
an electron and an antineutrino.
a positron and a neutrino.
an electron and a neutrino.
A.
0
2. Which of the following graphs shows the variation
with mass m of the activity of a sample of a
radioactive material?
A.
B.
activity
C.
C.
0
D.
activity
D.
0
E
activity
0
m
E
0
0
E
0
0
B.
E
0
m
0
0
0
7. When electrons of suitable energy travel through a
thin layer of graphite, a pattern of concentric
circles is produced on a screen.
activity
fine beam of electrons
0
0
m
0
0
3. The Bohr model of the hydrogen atom is able to
A.
predict accurate values for some of the
wavelengths in the spectrum of atomic
hydrogen.
B.
account for the detailed structure of the spectral
lines in the spectrum of atomic hydrogen.
C.
explain the relative intensity of the different
spectral lines in the spectrum of atomic
hydrogen.
D.
be extended to predict accurately, some of the
wavelengths in the spectrum of oxygen.
4. Which one of the following is a correct definition
of the decay constant of a radio-isotope?
A.
The constant of proportionality linking half-life
to rate of decay of nuclei.
B.
The constant of proportionality linking decay
rate to number of undecayed nuclei.
C.
The reciprocal of the half-life of the radioisotope.
D.
The rate of decay of nuclei in a fresh sample of
the radio-isotope.
5. The following are statements concerning
radioactive decay.
I. Alpha particles have discrete energies.
II. The beta-energy spectrum is a broad continuous
distribution of energies.
III. Gamma rays are emitted with discrete energies.
Which statement(s) is(are) evidence for the existence
of nuclear energy levels?
A.
I only
B.
II only
C.
III only
D.
I and III only
m
graphite
fluorescent screen
The production of this pattern is evidence for
A.
the wave nature of the electron.
B.
the nuclear model of the atom.
C.
the particle nature of the electron.
D.
the existence of X-rays.
8. The work function of a metal may be defined as
A.
the minimum frequency of the incident
electromagnetic radiation required to
cause photoelectric emission.
B.
the minimum wavelength of the incident
electromagnetic radiation required to
cause photoelectric emission.
C.
the minimum energy of photons incident
on a surface required to cause
photoelectric emission.
D.
the minimum energy required to take an
electron from the interior to the surface to
cause photoelectric emission.
9. In a mass spectrograph, ions of isotopes of the same
element follow different semicircular paths in a
uniform magnetic field as shown.
ions
The difference in path curvature could be due to the
fact that the ions have different values of
A. charge only.
B. charge and speed.
C. mass and charge.
D. mass and speed.
10. Some of the energy levels of the hydrogen atom
Electrons are excited to the 0.85 eV level. How
are shown below. (not to scale)
many different photon frequencies will be
–––––––––––––– – 0.54 eV
observed in the emission spectrum of hydrogen?
–––––––––––––– – 0.85 eV
A.
3
B.
4
–––––––––––––– – 1.51 eV
C.
5
D.
6
–––––––––––––– – 3.39 eV
–––––––––––––– – 13.6 eV
Short Answer questions Write your response in the space provided
11.
Light is incident on a clean metal surface in a vacuum. The maximum kinetic energy KEmax of the electrons
ejected from the surface is measured for different values of the frequency f of the incident light.
The measurements are shown plotted below.
2.0
1.5
KEmax / × 10–19 J 1.0
0.5
0.0
4.0
4.5
5.0
5.5
6.0
6.5
7.0
7.5
8.0
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(a)
f / × 10 Hz
Draw a line of best fit for the plotted data points.
(1)
(b) Use the graph to determine
(i) The Planck constant.
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(2)
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(ii) The minimum energy required to eject an electron from the surface of the metal (the work function).
(3)
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(c) Explain briefly how Einstein’s photoelectric theory accounts for the fact that no electrons are emitted from
the surface of this metal if the frequency of the incident light is less than a certain value.
(3)
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12.
This question is about the wave nature of electrons.
(a) Describe the de Broglie hypothesis.
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(2)
2
An experiment is carried out in which a beam of electrons is scattered from a single nickel crystal. A
schematic diagram of the apparatus is shown below.
Vacuum
Nickel
crystal
Incident
electron beam
Electron “gun”
Scattered electron beam
The electrons are accelerated in the electron “gun” by a potential difference of 75 V.
(b) Determine the wavelength associated with the electrons as predicted by the de Broglie hypothesis.
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(4)
The number n of electrons scattered per second through an angle θ is measured. The graph below shows
the variation with angle θ of n.
n
0
0
(c) Suggest how the shape of this graph supports the de Broglie hypothesis.
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13.
Diagram 1 shows part of the emission line spectrum of atomic hydrogen. The wavelengths of the principal
lines in the visible region of the spectrum are shown.
Diagram 2 shows some of the principal energy levels of atomic hydrogen.
(a) Show, by calculation, that the energy of a photon
Diagram 1
Diagram 2
of red light is 1.9 eV.
Red (R)
Blue (B) Violet (V)
........................................................................................
0
–0.54
–0.85
–1.5
656 nm
486 nm 434 nm
–3.4
wavelength
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(b)
(i)
On Diagram 2, draw arrows to represent:
The electron transition that gives rise to the
red line (label this arrow R).
(ii)
A possible electron transition that gives rise to
the blue line (label this arrow B).
Energy / eV
(1)
–13.6
(1)
3
14. (a) The half-life of a radioactive isotope is 10 days. Calculate the fraction of the sample that remains after 25
days.
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(b) A radioactive material has a half-life of 6.02 hours. If the original activity is 640 Bq, calculate the activity
after 8 hours.
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(c) A 1.49 µg sample of 13N7 has a half-life of 10 minutes.
(i) How many nuclei are present initially? Avogadro’s number = 6.02 x 1023.
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(ii) What is the initial activity?
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(iii) What is the activity after 1 hour?
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(iv) After how long will the activity be less than 1 per second?
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