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§D. Photo-electrons are emitted by a clean metal surface only when the
incident light exceeds a minimum
A. wavelength
B. intensity
C. photon density
D. frequency
§C. Which one of the following transitions in a hydrogen atom emits the
photon of the highest frequency ?
A. n = 1 to n = 2
B. n = 2 to n = 6
C. n = 2 to n = 1
D. n = 6 to n = 2
§D. The de Broglie wavelength associated with an electron moving with a
speed half that of light in a vacuum, where the usual symbols are
used, is
A. mc2/4
B. mc/2h
C. e/m
D. 2h/mc
§B. The total number of protons and neutrons in the nucleus
A. 26
B. 56
C. 30
D. 82
56
26
Fe is
14
§B. When 6 C decays into 147 N the radiation emitted is
A. one alpha particle
B. one beta particle
C. one gamma ray photon
D. one alpha particle with gamma radiation
§A. The process by which a heavy nucleus splits into two lighter nuclei is
known as
A. fission
B. fusion
C. beta decay
D. a chain reaction
§A. A charged oil drop of mass m is balanced between horizontal parallel
metal plates separated by a distance d and with a potential difference
V. The charge on the drop must be
A. mgd/V
B. mgV/d
C. V/mgd
D. d/mgV
§D. In Rutherford’s scattering experiment, a stream of alpha particles is
fired at a thin gold foil. Most of the alpha particles
A. are scattered randomly
B. rebound
C. are scattered uniformly
D. go though the foil
§B. A piece of radioactive material now has about 1/16 of its previous
activity. If its half-life is 4 hours the difference in time between
measurements is approximately
A. 8 hours
B. 16 hours
C. 32 hours
D. 60 hours
§C. Which of the following phenomena provides evidence for the wave
nature of matter ?
A. The line spectra of atomic hydrogen.
B. The photo-electric effect.
C. The diffraction of electrons by crystals.
D. Beta decay.
§C. Which one of the following gives the correct order of magnitude of the
minimum energy in MeV of a gamma ray that could produce an
electron-positron pair ?
A. 10-2
B. 10-1
C. 1
D. 10
§B. The following data points show how the activity of a sample of a
radioactive nuclide varies with time
activity
/min
-1
600
500
400
300
200
100
2
4
6
8
10 12 14 16
time /min
The best estimate of the half-life of the sample is
A. 2·0 mins
B. 3·0 mins
C. 5·0 mins
D. 7·0 mins
§B. An electron enters a region with both electric and magnetic fields and
remains undeflected, as shown in the diagram below.
Which one of the lines in the table below shows the direction of the
electric and magnetic fields ? (Line PQ represents a direction at 90° to
the plane of the diagram.)
A.
B.
C.
D.
Electric field
from P to Q
from P to Q
from P to Q
from P to Q
Magnetic Field
from Q to P
from S to R
from S to R
from P to Q
§B. When light is incident on a metal surface, electrons may be ejected.
The following graph shows the variation with frequency f of the
maximum kinetic energy MKE of the ejected electrons.
MKE
0
f
Which one of the following graphs best shows the variation with
frequency f of the maximum kinetic energy MKE of the ejected
electrons if another metal surface with a lower threshold frequency is
used ?
A
B
MKE
MKE
0
f
f
C
D
MKE
MKE
0
f
f
§D. The following are statements about radioactive decay.
Alpha particles have discrete energies.
The beta-energy spectrum is a broad continuous distribution of
energies.
III. Gamma rays are emitted with discrete energies.
I.
II.
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
§C. Some of the energy levels of the hydrogen atom are shown below.
-0·54 eV
-0·85 eV
-1·51 eV
-3·39 eV
Electrons are excited to the 0·85 eV level. How many different photon
frequencies will be observed in the emission spectrum of hydrogen ?
A. 3
B. 4
C. 5
D. 6
§A. When electrons of suitable energy travel through a thin layer of
graphite, a pattern of concentric circles is produced on a screen.
fine beam of
electrons
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.
§A. X rays can be produced by the collision of high energy electrons with
A. a metal
B. a gas
C. photons
D. neutrinos.
§B. In a mass spectrograph, ions of isotopes of the same element follow
different semicircular paths in a magnetic field as shown below.
The difference in the path curvature is essentially due to the fact that
the ions have different values of
A. charge only.
B. mass only.
C. mass and charge.
D. mass and speed.
§B. The reaction
n

p
+
e-
never occurs because it violates the law of conservation of
A. baryon number only.
B. lepton number only.
C. electric charge only.
D. baryon number and electric charge only.
§C. A nucleus of mass M has Z protons, each of mass mP, and N neutrons
each of mass mn. Its binding energy is given by
A. (ZmP - M) c2
B. (M + ZmP + Nmn) c2
C. (ZmP + Nmn - M) c2
D. (ZmP + Nmn) c2
§B. The diagram below, which is drawn to scale, shows some of the
atomic energy levels of a fictitious element. The three transitions
shown result in radiation in the ultraviolet (UV), red and yellow regions
of the spectrum. Which one of the choices below correctly identifies
the transitions ?
Q
R
S
UV
red
yellow
A.
Q
R
S
B.
S
R
C.
R
Q
S
Q
D.
S
R
Q
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