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*P16*
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PRE-LEAVING CERTIFICATE EXAMINATION, 2007
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PHYSICS — HIGHER LEVEL
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TIME: 3 HOURS
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Answer three questions from section A and five questions from section B.
Page 1 of 10
SECTION A (120 marks)
Answer three questions from this section.
Each question carries 40 marks.
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1.
In an experiment to verify Boyle’s law, a student obtained the following values of pressure
and volume for a fixed mass of gas:
P/kPa
100
120
140
160
180
200
220
V/cm3
24.0
20.1
17.0
15.1
13.2
11.9
10.9
Draw a labelled diagram of the apparatus the student might have used.
Draw a suitable graph to verify Boyle’s law.
(9)
(18)
What two features of the graph verify Boyle’s law?
(6)
Outline two steps the student might have taken to ensure that the temperature of the gas
remained constant.
(7)
2.
A student carried out an experiment to measure the specific latent heat of fusion of ice.
Ice was added to water in a copper calorimeter. The following results were obtained:
Mass of calorimeter
80 g
Mass of water
120 g
Initial temperature of water
29o C
Temperature of ice
0o C
Mass of ice
25.3 g
Final temperature of water
11o C
The specific heat capacities of copper and water are 390 J kg–1 K–1 and 4180 J kg–1 K–1
respectively.
Use this data to calculate a value for the specific latent heat of fusion of ice.
(18)
What two things did the student do to the ice before adding it to the water?
Explain why these were necessary.
(12)
How was the value of the mass of ice obtained?
(6)
Outline any other way the student improved the accuracy of the result.
(4)
Page 2 of 10
3.
In an experiment to measure the focal length of a concave mirror, a student first obtained an
approximate value.
She then used some laboratory apparatus to find a series of values of image and object
distances, which she used to calculate a more accurate value for the focal length.
The following are the sets of values she obtained for the object distance u and the image
distance v:
u/cm
50.0
45.0
40.0
35.0
30.0
25.0
v/cm
33.3
36.1
39.2
46.9
59.7
99.0
Explain how the student might have obtained an approximate value of the focal length.
(7)
Describe, with the aid of a labelled diagram, how the student might have arranged the
apparatus to obtain the above data.
(9)
Explain how the position of the image was obtained.
(6)
Use all the data to calculate a value for the focal length, f.
4.
(18)
A student carried out an experiment to investigate the variation of the resistance of a
thermistor with temperature. The table shows the values obtained.
Temperature/o C
0
10
20
30
40
50
60
70
80
Resistance/kΩ
12.0
8.0
5.7
4.5
3.3
2.8
2.4
2.1
1.9
Draw a labelled diagram of the apparatus used in the experiment.
How did the student obtain values for the resistance?
Plot a graph, on graph paper, of the resistance against the temperature.
(10)
(6)
(12)
From the graph, estimate the temperature when the value of the resistance is 4 kΩ.
(3)
What is the resistance when the temperature is 5o C?
(3)
Outline two ways to improve the accuracy of this experiment.
(6)
Page 3 of 10
SECTION B (280 marks)
Answer five questions from this section.
Each question carries 56 marks.
_______________
5.
Answer any eight of the following parts (a), (b), (c), etc.
(a)
State Newton’s law of universal gravitation.
(b)
A wooden block of weight 490 N floats in water. What weight of water does it displace?
(7)
(c)
A 150 W electric motor raises a 5 kg block through a height of 2 m in one second.
What is the percentage efficiency of the motor? (acceleration due to gravity is 9.8 m s–2)
(7)
(d)
Two thermometers do not necessarily give the same reading at the same temperature.
Explain why this may happen.
(7)
(e)
What is meant by the term solar constant?
(f)
The frequency of a siren is 1000 Hz. It moves towards an observer at a speed of
100 m s–1. The speed of sound is 340 m s–1. What is the apparent frequency as heard
by the observer?
(7)
(g)
The critical angle for diamond is 24.4o. What is its refractive index?
(7)
(h)
Two equal positive charges of 50 mC are placed 2 metres apart in a vacuum.
What force do the charges exert on one another?
(permittivity of free space = 8.9 × 10–12 F m–1)
(7)
(i)
State Faraday’s law of electromagnetic induction.
(7)
(j)
Explain the difference between nuclear fission and nuclear fusion.
(7)
Page 4 of 10
(7)
(7)
6.
Define the terms (i) velocity, (ii) acceleration.
(6)
A body travels in a straight line with constant acceleration. Derive an expression for the
displacement of the body in terms of its initial velocity, its acceleration and the time of
travel.
(9)
The graph shows how the velocity of a lift in a hotel changes with time:
Upward velocity / m s-1
66
5
45
3
24
1
0
3 0
0
(i)
(ii)
(iii)
(iv)
(v)
(vi)
7.
1
1
2
2
3
3
4
4
5
6
5
7
Time / s
Describe the motion of the lift during the first two seconds.
Find the acceleration of the lift during the first two seconds.
The lift is slowing down between A and B (the third and seventh second).
How far does it travel during this time?
How far does the lift travel between the start and end of its motion?
What is the average velocity of the lift?
A child in the lift drops a coin from one metre above the lift floor just as the lift
begins to move. How long does the coin take to fall to the floor?
(acceleration due to gravity = 9.8 m s–2)
Explain the terms (i) interference, (ii) diffraction.
(6)
(6)
(9)
(6)
(6)
(8)
(12)
Visible light is part of the electromagnetic spectrum. What name is given to the part of the
spectrum with wavelength just shorter than visible light?
(6)
How can this radiation be detected?
(6)
Infrared radiation can be used in night vision goggles. Give one other application of
infrared.
(6)
x
θ
laser
1m
diffraction
diffraction
grating
screen
The apparatus shown was set up to determine the wavelength of laser light. The n = 0 and
n = 1 bright spots are shown. The screen was placed 1 metre from the diffraction grating,
which had 100 lines per mm.
What is the separation, d, of the lines on the grating?
(6)
If the distance x is 6.8 cm, what is the value of the angle θ?
(6)
Find a value for the wavelength, λ.
(9)
Name one common use of a laser in the home.
(5)
Page 5 of 10
8.
Pure silicon is semiconductor. When a voltage is applied across a silicon wafer, intrinsic
conduction can take place.
Explain the underlined terms.
(12)
The table shows the number of outer electrons in the atoms of certain
elements. What type of semiconductor is formed when pure silicon is
doped with Indium? Explain your answer.
(12)
Silicon
Arsenic
Indium
4
5
3
How is a p-n junction formed? Explain why a p-n junction
causes a layer in which there are no free charge carriers. (12)
The diagram shows a diode connected to an a.c. supply.
Sketch a graph to show how the voltage across the resistor
varies with time.
(9)
The output is said to be rectified. Name one device where a diode is used in this way.
(3)
LEDs are often used instead of filament bulbs. Give two advantages of the LED over the
filament bulb. Explain why an LED will not light if it is connected the wrong way round.
(8)
9.
The graph represents the activity of a radioactive sample monitored over 16 days.
The activity was measured at the same time each day.
Explain the term background radiation.
(6)
Counts
Counts per
per
minute
What is the approximate background radiation
in the region where the above readings were
taken?
(6)
Explain the term half-life.
(6)
What is the approximate half-life of this
sample?
2200
2200
2000
2000
1800
1600
1800
1400
1200
1600
(6)
What is the decay constant for the sample? (9)
Name an instrument that could have been used
to detect the radioactivity of the sample.
(6)
1000
1400
800
600
1200
400
200
1000
0
0
2 24
64
8
6
10
12 8 14
Time inin
10 Time
16
days
What is a becquerel?
(6)
Express the first activity noted on the graph in terms of becquerels.
(5)
Name two common sources of background radiation.
(6)
Page 6 of 10
10.
Answer either part (a) or part (b).
(a)
“By combining the quarks in various ways all the mesons and baryons in the Particle
Zoo can be constructed. The leptons are not composed of quarks and are
fundamentally indivisible.”
What Irish writer coined the term quark?
(3)
How many families (or generations) of quarks are there?
(3)
In our everyday world we usually encounter only two quarks; name them.
(6)
What is meant by the Particle Zoo?
(6)
Give one difference between mesons and baryons.
(3)
Name a baryon.
(3)
The proton is composed of three quarks: uud. What is the quark composition of the
neutron?
(6)
The electron is not composed of quarks. Explain why.
(6)
What fundamental force do leptons not feel?
(6)
Which one of the following particles is not a lepton?
muon
neutrino
pion
positron
(5)
A beam of charged π-mesons is travelling at one-third of the speed of light.
What is the average distance travelled before decay?
(Mean life of π-meson = 2.6 × 10–8 s; speed of light: c = 3 × 108 m s–1)
(b)
(9)
A current in a magnetic field experiences a force. This is the principle of operation of
the moving-coil galvanometer.
What is a galvanometer?
(6)
Name two devices, other than meters, based on the same principle.
(6)
How is a galvanometer converted to an ammeter?
(3)
A galvanometer has a coil of resistance 100 Ω and a full-scale deflection of 2 mA.
Calculate the resistance required to convert it to an ammeter reading up to 1 A. (9)
The diagram shows an electromagnetic relay.
Explain what happens in both circuits when
the switch is closed.
(9)
What is the advantage of using a relay?
(6)
Name two places where you would expect
to find a relay.
(6)
A diode is often used for protection in circuits
containing a relay. Explain why the diode
might be necessary.
(6)
The relay can be thought of as a basic amplifier.
Name another device that can act as an amplifier.
(5)
Page 7 of 10
11.
Read the following passage and answer the accompanying questions.
The discovery of X-rays was one of those lucky scientific ‘accidents’ and was the
result of experiments on cathode rays carried out by Wilhelm Roentgen (1845
– 1923) of Germany. Roentgen was Professor of Physics at Würtzburg.
In England, at the time, cathode rays were considered to be particles but German
scientists favoured some kind of ray. One way of detecting cathode rays is to make
use of their property of causing fluorescence. In 1895 Roentgen was working with
a cathode ray tube when he noticed an unexpected glow about two metres away
from the tube, coming from some barium platinocyanide, a fluorescent material
that was often used to detect cathode rays.
The effect could not have been caused by the cathode rays, as it was known that
they have a range in air of only a few centimetres. He knew that it had to be a
different phenomenon – but what?
He spent the next seven weeks investigating this unknown radiation. He discovered
that human flesh is transparent to it, but that bones are not. He produced a
photograph showing the bones of the hand of his wife Bertha. Not yet knowing
what kind of rays they were, he called them X-rays.
(a)
(b)
We know now that cathode rays are beams of particles. What type of particles are they?
(7)
What is fluorescence?
(7)
(c)
What is thermionic emission?
(d)
X-rays are a form of ionising radiation. Name another type of ionising radiation. (7)
(e)
Give two ways in which ionising radiation can be hazardous to humans.
(7)
(f)
X-ray production may be thought of as the inverse of the photoelectric effect.
Give two reasons to support that idea.
(7)
(7)
(g)
X-rays are produced by accelerating electrons to high speeds. If the accelerating
voltage is 40 kV, with what speed do the electrons strike the target?
(charge on the electron = 1.6 × 10–19 C, mass of electron = 9.1 × 10–31 kg)
(7)
(h)
Give one industrial use of x-rays.
Page 8 of 10
(7)
12.
Answer any two of the following parts (a), (b), (c), (d).
(a)
State Newton’s second law of motion.
(7)
Two cars approach one another on a straight road and collide. Car A has a mass of
1200 kg and a speed of 18 m s–1. Car B has a mass of 1000 kg and a speed of 10.8 m s–1
in the opposite direction.
18 m s–1
10.8 m s–1
If the cars lock together on impact, find their combined speed after the collision. (12)
(b)
(c)
If the impact lasts for 0.3 s, what force does each car exert on the other?
(9)
What is meant by the term temperature?
(6)
What is the SI unit of temperature?
(3)
Give an expression that defines temperature in degrees Celsius.
(9)
What do you understand by the term a thermometric property?
(6)
Give two examples of a thermometric property.
(4)
Voltmeters are connected across
a resistor and a capacitor as shown.
(i)
Calculate the current immediately
after the switch is closed.
(7)
(ii)
When the current in the circuit is
10 mA what is the reading on
the voltmeter connected across
the resistor?
(7)
(iii)
When the current in the circuit is 10 mA what is the reading on the voltmeter
connected across the capacitor?
(7)
(iv)
Find the energy stored in the capacitor when it is fully charged.
Page 9 of 10
(7)
(d)
What is meant by atomic number?
(6)
What is meant by mass number?
(6)
What are isotopes?
(6)
Give two uses of radioactive isotopes.
(6)
226
A nucleus of radium can be represented by
88
How many neutrons are there in this nucleus?
Page 10 of 10
Ra
.
(4)