Multiple Choice
Identify the
choice that best completes the statement or answers the question.
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1.
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The relation between light and the electromagnetic
field has been explained by Maxwell for the first time. Which one of the following statements is
true?
A | The speed of light depends on the motion of the
ether | B | The speed of light is dependent on the electrical
properties of the particles inside the medium | C | The speed of light
is an absolute universal constant that does not depend on the medium | D | The speed of light is an absolute constant for a given medium and depends only
on the medium. |
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2.
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Ana and Jim are discussing the relation between the
Galilean relativity and Einstein’s relativity. They are analysing an experiment in which two
observers measure the speed of light. One observer is on Earth and the other one is in a superfast
train. Ana says that according to the special relativity the light will be found to have the same
speed by both observers. Jim says that they will find different speeds because of the train that is
in motion. Which one is correct?
A | Ana is correct as the speed of light is an invariant for
any observer and this is in contradiction to the Galilean relativity | B | Ana is correct as the speed of light is the same in any frame of reference
according to the Galilean relativity | C | Jim is correct as
the speed of light measured by the stationary observer is faster than the one measured by the
observer on the train | D | Jim is correct as
predicted by Einstein in the Special Theory of Relativity |
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3.
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The fact that the speed of light is the same in any
frame of reference and anyone measuring it will find the same value leads to a very unusual
conclusion regarding the time:
A | Time passes in the same way in any frame of
reference | B | Time is relative to the frame of reference; however
events that are simultaneous in one frame of reference are simultaneous in any frame of
reference | C | Time passes slower on the frame of reference that is in
motion | D | Time passes faster on the frame of reference that is in
motion |
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4.
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Which one of the following statements about the
speed of light is false?
A | Light in a vacuum moves faster than any material
body | B | Shadows made by light can move a lot faster than the
speed of light | C | Light has momentum.
It can hit bodies and put them in motion | D | Light has a small
rest energy, which varies with its frequency |
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5.
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On Jan 1, 2354 two astronauts depart from Earth
travelling at 0.95 of the speed of light with respect to the Earth. What year is it on Earth after
they have travelled one year in their frame of reference?
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6.
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While travelling, they pass an alien in a space
ship, moving in the same direction, but at only 0.4c. At the time, one is standing at the front of
the ship, holding a green light, the other at the back, holding a red light. When they are both
equidistant from the alien, a light midway between them flashes, and turns on both of their lights
simultaneously, in their frame of reference. Which light does the alien see first?
A | The red light, because the alien sees it as travelling
towards the light that flashes | B | The green light,
because red light travels slower than green light | C | Both at the same time, because simultaneous events have zero time between
them, and zero times the time contraction factor is still zero | D | The green light, because the alien sees it as travelling towards the light
that flashes |
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7.
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Time travel is one of the most exciting topics for
science-fiction. Which one of the following statements regarding time travel is true?
A | Time travel to the past is possible as long as we do not
change the past and we are just simple observers | B | Time travel to the past is impossible and this is a consequence of the fact we
can not pass the speed of light | C | Time travel to the
future is impossible | D | Time travel to the
future is possible but there is no coming back |
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8.
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A relativistic train is 100 m in length and fits
exactly in a train station with the same size. One of the trains does not stop in all stations and
just passes by at 0.8 of the speed of light. What is the train length as seen by a passenger waiting
at the station?
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9.
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What was the purpose of the Michelson-Morley
experiment?
A | To demonstrate the existence of the ether by measuring
the speed of light at different points on the orbit of the Earth around the
Sun. | B | To show that the speed of light is
constant. | C | To measure the speed of the Earth around the
Sun. | D | To measure the speed of the
ether. |
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10.
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What was the conclusion of the Michelson-Morley
experiment?
A | The ether exists and it is a very fine medium filling up
the whole universe. | B | The speed of light
measured when the Earth was moving in opposite directions was exactly the same proving the
inexistence of the ether. | C | The ether does not
exist as the speed of light was found to be different when measured when the Earth was moving in
opposite directions. | D | The ether exists
because the speed of light was found to be an absolute
constant. |
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11.
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The relativity of simultaneity of two events
happening at different points in space is another surprising conclusion of Einstein’s new
theory of relativity. Which of the following statements is true?
A | Two events that are simultaneous in one frame of
reference will be simultaneous in any frame of reference in the Universe. | B | If two events are observed to occur in one order as measured by one frame of
reference they could not be observed to occur in reverse order by another frame of
reference. | C | Two events could be simultaneous in one frame reference
and not simultaneous in another frame of reference that is moving with respect to the first
one. | D | Two events can never be
simultaneous. |
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12.
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Nuclear energy is one of the most powerful forms of
energy known to us. If it was to be possible to convert water entirely into pure energy, what amount
of water would we need to satisfy the energy needs of Australia in one year? (Consider
Australia’s energy needs in one year to be 4  1018J.)
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13.
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Would it be possible for a mother to become younger
than her son according to the Special Theory of Relativity?
A | No, this is impossible. Time can travel slower, but it
can’t run backwards. | B | No this is
impossible because the mother is older than the son | C | Yes it would be possible if the mother went on space trip at a speed very
close to the speed of light. | D | Yes it would be
possible if the son went on space trip at a speed very close to the speed of
light. |
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14.
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A spaceship has accelerated to 99.999% of the speed
of light. What is the distance travelled by the ship in one day (time measured on the
ship)?
A | 6.7  1010
m | C | 5.8  1012
m | B | 5.8  1015
m | D | 1.9  107 m |
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15.
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How long in ship’s time would it take to go
across the Milky Way galaxy? (100,000 light years in diameter - 1 light year = 9.46 
1015m)
A | 223 years | C | 201
days | B | 447 years | D | 1 million
years |
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16.
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The Lorentz factor of a muon in motion is 20. What
is the speed of the muon as a fraction of the speed of light?
A | 99.8 c | C | 99.0%
c | B | 1.0001 c | D | 0.998
c |
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17.
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What is the mass of an electron accelerated at a
speed of 99.995% of c?
A | 9.1  10-34
kg | C | 9.1  10-29
kg | B | 9.1 mg | D | 9.1 
10-31 kg |
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18.
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How many times is the motion mass of the electron
in question 17 greater than its rest mass?
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19.
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A group of physics student is visiting the
Australian Synchrotron. The teacher that guides them asks the students to calculate the kinetic
energy of an electron at the end of the LINAC, at a speed of 99.995% of the speed of light. One
student uses Newtonian physics to calculate the value. What is his answer?
A | 4.1  10-14
J | C | 0.2  10-15
J | B | 1.4  10-22
J | D | 8.1  10-12
J |
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20.
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Another student uses the Special Theory of
Relativity to perform the task given by the teacher in question 19. What is his answer?
A | 4.1  10-14
J | C | 0.2  10-15
J | B | 1.4  10-22
J | D | 8.1  10-12
J |
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