OXFORD CAMBRIDGE AND RSA EXAMINATIONS
Advanced Subsidiary GCE
PHYSICS A
Electrons and Photons
Friday
9 JUNE 2006
2822
Morning
1 hour
Candidates answer on the question paper.
Additional materials:
Electronic calculator
TIME
1 hour
INSTRUCTIONS TO CANDIDATES
•
Write your name, Centre Number and Candidate number in the boxes above.
•
Answer all the questions.
•
Read each question carefully and make sure you know what you have to do before starting your
answer.
•
Write your answers, in blue or black ink, in the spaces provided on the
question paper.
•
Pencil may be used for graphs and diagrams only.
•
•
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Qu.
Max
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INFORMATION FOR CANDIDATES
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The number of marks is given in brackets [ ] at the end of each question
or part question.
•
You will be awarded marks for the quality of written communication where
this is indicated in the question.
•
You may use an electronic calculator.
•
You are advised to show all the steps in any calculations.
This question paper consists of 14 printed pages and 2 blank pages.
SP (SLM/SLM) S94229/3
© OCR 2006 [T/100/3701]
Registered Charity Number: 1066969
[Turn over
Mark
2
Data
speed of light in free space,
c = 3.00 × 10 8 m s –1
permeability of free space,
0 = 4 × 10 –7 H m–1
permittivity of free space,
0 = 8.85 × 10 –12 F m–1
elementary charge,
e = 1.60 × 10 –19 C
the Planck constant,
h = 6.63 × 10 –34 J s
unified atomic mass constant,
u = 1.66 × 10 –27 kg
rest mass of electron,
me = 9.11 × 10 –31 kg
rest mass of proton,
mp = 1.67 × 10 –27 kg
molar gas constant,
the Avogadro constant,
R = 8.31 J K –1 mol –1
NA = 6.02 × 10 23 mol –1
gravitational constant,
G = 6.67 × 10 –11 N m 2 kg –2
acceleration of free fall,
g = 9.81 m s –2
3
Formulae
uniformly accelerated motion,
s = ut +
1
2
at 2
v 2 = u 2 + 2as
1
sin C
refractive index,
n=
capacitors in series,
1
1
1
=
+
+...
C C1 C2
capacitors in parallel,
C = C1 + C2 + . . .
capacitor discharge,
x = x0e–t/CR
pressure of an ideal gas,
p=
radioactive decay,
x = x0e– λt
1
3
Nm 2
<c >
V
t = 0.693
λ
critical density of matter in the Universe,
relativity factor,
3H02
ρ0 =
8G
= √ (1 –
current,
I = nAve
nuclear radius,
r = r0A1/3
sound intensity level,
= 10 lg
v2
)
c2
( )
I
I0
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4
A ns we r all the questions.
1
(a)
Fig. 1.1 shows an electrical circuit.
A diagram has been removed due to third party copyright
restrictions
Details: A diagram of an electrical circuit showing positive
and negative ions in a conducting liquid with a circuit going
into the liquid
Fig. 1.1
(i)
The directions of flow of ions in the liquid are shown. On Fig. 1.1, draw an arrow at
s how the dire c tion of the e le c tron flow in the wire .
(ii)
State what is meant by conventional current .
X to
[1 ]
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(iii)
A charge of 0.76 C flows past point
the wire.
X in a time of 5.0 minutes. Calculate the current in
c urre nt = . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A [3 ]
5
(b) Fig. 1.2 shows a magnetic compass placed very near a current-carrying wire and in a plane
at right angles to the wire. The compass needle aligns itself in the direction of the magnetic
field due to the current in the wire.
conventional current
compass
P
Fig. 1.2
State and explain the effect, if any, on the compass needle when the compass is placed at
point P.
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[Total: 7]
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2
State three main features common to all types of radiations in the electromagnetic spectrum.
Name three principal radiations in the electromagnetic spectrum other than visible light. For one
of these radiations, give a useful application.
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[Total: 7]
7
3
Fig. 3.1 shows a rectangular block of electrically conducting material.
9.0 cm
1.2 cm
1.2 cm
X
Y
Fig. 3.1
(a) The conducting block obeys Ohm’s law. State Ohm’s law, in words.
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(b) When the ends X and Y of the block are connected to a 0.15 V d.c. supply of negligible internal
resistance, the current drawn is 4.3 A.
(i)
Show that the block has a resistance of 3.5 × 10–2 Ω.
[1]
(ii)
Calculate the resistivity of the material.
resistivity =.................................... unit ........... [4]
[Total: 7]
[Turn over
8
4
Fig. 4.1 shows an arrangement of three filament lamps used to illuminate a room.
A photograph has
been removed due to
third party copyright
restrictions
Details: A photograph of
three lights on a ceiling
12 V
equivalent
to
Fig. 4.1
(a)
Name the arrangement in which the three lamps are connected.
...............................................................................................................................................[1]
(b) Each lamp has resistance 8.0
Ω when operating at 12V.
Calculate
(i)
the current drawn by each lamp
c urre nt = . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A [2 ]
(ii)
the power dissipated by each lamp
powe r = . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . W [3 ]
(iii)
the total resistance of the lamps as connected in Fig. 4.1
re s is ta nc e = . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ω [3]
9
(iv)
the total energy transformed by the three lamps in kilowatt hour when operated for 12
hours.
energy = .......................... kW h [2]
(c) One of the lamps is replaced by another lamp that also operates at 12 V but has a smaller
resistance than 8.0 Ω. State and explain how its brightness will compare with one of the other
two remaining lamps.
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[Total: 13]
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10
5
(a) Complete the following sentence for a statement of Kirchhoff’s first law.
The sum of the ..................................... into a point in a circuit is equal to the sum of the
..................................... out from that point.
[1]
(b) Complete the following statement about Kirchhoff’s second law.
In an electrical circuit, the sum of the e.m.f.s around a closed loop is equal to the sum
of the p.d.s around the same loop. This is a consequence of conservation of
..................................... .
[1]
(c) Fig. 5.1 shows a part of an electrical circuit.
0.032 A
P
0.006 A
I
700 Ω
E
200 Ω
Fig. 5.1
(i)
Name the component P.
.......................................................................................................................................[1]
(ii)
State how the resistance of component P is affected by a change in its temperature.
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11
(iii)
At a particular temperature, the currents are as shown in Fig. 5.1. Use Kirchhoff’s laws to
determine
1
the current I in the 200 Ω resistor
I = ................................ A [1]
2
the e.m.f. E of the cell.
E = ................................ V [3]
[Total: 8]
[Turn over
12
6
Fig. 6.1 shows a zinc plate attached to a charged gold-leaf electroscope. The arrangement is used
to demonstrate the photoelectric effect.
ultra-violet
radiation
negatively charged
zinc plate
insulator
metal stem
gold leaf
Fig. 6.1
The zinc plate, metal stem and gold leaf have an excess of electrons. This causes the leaf to
deflect away from the stem.
(a) When the zinc plate is exposed to high frequency ultra-violet radiation, it loses electrons from
its surface and consequently the gold leaf falls rapidly. If the demonstration is repeated with
visible light, the leaf does not fall.
Use the photoelectric effect to describe how the ultra-violet radiation interacts with the surface
electrons of the zinc plate. Explain why visible light, no matter how intense, does not release
electrons from the zinc plate.
In this question, two marks are available for the quality of written communication.
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Quality of Written Communication [2]
13
(b) Ultra-violet radiation of wavelength 3.9 × 10–7 m is incident on the surface of a metal plate.
The maximum kinetic energy of an emitted photoelectron is 1.5 eV.
Calculate
(i)
the maximum kinetic energy of a photoelectron in joules
kinetic energy = .................................J [2]
(ii)
the work function energy of the metal in joules.
work function energy = .................................J [3]
[Total: 12]
7
(a) The table below shows four statements that may or may not be true about the wave-nature
of the electron. Place a tick (✓) next to the statement if it is correct and a cross ( ) if it is
incorrect.
Place a ✓ or
a here
Electrons can be diffracted by matter. This confirms their wave nature.
The wavelength of the electron is given by the de Broglie equation.
The wave associated with a moving electron is an electromagnetic wave.
The kinetic energy of the electron is given by the equation E = hf.
[3]
(b) Calculate the speed of a carbon atom of mass 2.0 × 10–26 kg travelling in space with a de
Broglie wavelength of 6.8 × 10–11 m.
speed = .......................... m s–1 [3]
[Total: 6]
END OF QUESTION PAPER
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Permission to reproduce items where third-party owned material protected by copyright is included has been sought and cleared where possible. Every reasonable
effort has been made by the publisher (OCR) to trace copyright holders, but if any items requiring clearance have unwittingly been included, the publisher will be
pleased to make amends at the earliest possible opportunity.
OCR is part of the Cambridge Assessment Group. Cambridge Assessment is the brand name of University of Cambridge Local Examinations
Syndicate (UCLES), which is itself a department of the University of Cambridge.
2822/01
Mark Scheme
June 2006
1
(a)(i) Correct direction shown (anticlockwise)
B1
(a)(ii) Direction in which positive charges / ions move /
Direction / flow / current / from positive to negative /
Flow of (positive) charge from positive to negative /
Direction / flow opposite to electron flow
B1
(a)(iii) Q = It
C1
(Allow any subject with or without delta notation)
0.76
5.0 × 60
current = 2.53 × 10-3 (A) ≈ 2.5 × 10-3 (A)
(0.152 / 0.15 (A) scores 1/3)
I=
(b)
C1
A1
The compass /needle points in the opposite direction
B1
(Magnetic) field is circular (about the wire) / in opposite direction / clockwise
B1
(Both marks can be scored on diagram)
[Total: 7]
2
Any three properties from:
(-1 for each error or contradiction)
1. Travel at the speed of light / c / 3 × 108 m s-1 (NOT ‘same speed’)
2. Travel through vacuum / ‘free space’
3. Have oscillating electric and magnetic fields
4. They are (all) transverse waves / can be polarised
5. Allow: ‘They show diffraction / reflection / refraction / interference’
6. Allow: ‘Consist of photons’
B1 × 3
Any three regions from the list below:
B1 × 3
Gamma (rays / radiation) / γ (rays) ; X-rays ; u.v ; ir ; microwaves ; radio waves
(NOT ‘radio’)
One suitable application for the opted region.
B1
(E.g.: Gamma rays for radiotherapy / sterilisation;
X-rays for taking pictures of skeleton / bones; u.v for tanning; ir for TV remote control;
microwaves for cooking / mobile phones; radio waves for communication)
(Note: Reference to alpha, beta and gamma can only score the last marking point)
[Total: 7]
11
2822/01
3
(a)
Mark Scheme
June 2006
current ∝ p.d / voltage (for a metallic conductor)
as long as temperature is constant / physical conditions remain constant
A1
(b)(i) (R =)
(b)(ii) R =
0.15
(= 0.0349)
4.3
M1
B1
ρL
(Allow any subject)
A
RA 0.035 × (0.012 × 0.012)
=
ρ=
L
0.09
resistivity = 5.6 × 10-5
A1
(Allow V m A-1)
unit: ohm metre / Ω m
A1
(5.6 × 10-n without unit or incorrect unit and n ≠ 5 or 3 – can score 2/4)
(5.6 × 10-3 Ω m – can score 3/4)
(5.6 × 10-3 Ω cm – can score 4/4)
C1
C1
[Total: 7]
4
(a)
(b)(i)
Parallel
B1
12
8.0
current = 1.5 (A)
I=
C1
A1
V2
(b)(ii) P =
/ P = IV / P = I 2 R
R
122
P=
/ P = 1.5 × 12
/ P = 1.5 2 × 8.0
8
power = 18 (W)
(b)(iii)
C1
(Possible ecf)
1
1
1
1
1 1 1 1
= +
+( ) /
= + +
R 8 8 8
R R1 R2
R3
1
1
= 3×
R
8
resistance = 2.67 ≈ 2.7 (Ω) (Allow answer expressed as 8/3)
(0.375 or 3/8 scores 2/3)
(b)(iv) energy = 0.018 × 12 × 3
energy = 0.648 ≈ 0.65 (kW h)
(0.22 (kW h) scores 1/2)
(648 (kW h) scores 1/2)
(2.3 × 106 (J) scores 1/2)
(Possible ecf)
12
C1
A1
C1
C1
A1
C1
A1
2822/01
(c)
Mark Scheme
It will be brighter
The current is larger / correct reference to: P ∝ 1 / R
B1
June 2006
B1
[Total: 13]
5
(a)
current and current
B1
(b)
energy
B1
(c)(i) (NTC) thermistor
B1
(c)(ii) Resistance decreases when temperature is increased. (ora)
(Allow correct credit for a PTC thermistor)
B1
(c)(iii)1
I = (0.032-0.006 =) 0.026 (A)
B1
(c)(iii)2
(V200 = 0.026 × 200 =) 5.2 (V) / (V720 = 0.006 × 700 =) 4.2 (V)
E = 5.2 – 4.2
(Allow E = 4.2 – 5.2)
E = 1.0 (V)
(Allow 1 sf answer)
(9.4 (V) scores 1/3)
C1
C1
A1
[Total: 8]
6
(a)
Maximum of three from points 1 to 6:
B1 × 3
1. Photon mentioned (e.g: photons interact with the surface electrons)
2. Energy is conserved (between the photon and the electron / in the interaction)
3. hf = φ + KE(max)
4. A single photon interacts with a single electron / It is a one-to-one interaction
5. Electron is removed when photon energy is greater than / equal to the work function
(energy) / φ
(Allow ora)
6. Electron removed when frequency is greater than / equal to the threshold
frequency
(Allow ora)
------------------------------------------------------------------------------------------7. (Visible) light has lower frequency than the threshold frequency / Energy of
(visible) light photon is less than the work function (energy) (ora with uv)
B1
8. Greater intensity of (visible) light means more photons (per unit time) /
energy of a photon remains the same
B1
QWC - Spelling, punctuation and grammar
QWC - Organisation
(b)(i) kinetic energy = 1.5 × 1.6 × 10-19
kinetic energy = 2.4 × 10-19 (J)
A1
B1
B1
C1
13
2822/01
(b)(ii) E = hf
/E =
hc
Mark Scheme
June 2006
/ f = 7.69 × 1014 (Hz) / (E =) 5.1 × 10-19 (J)
C1
λ
−19
φ = 5.1 × 10 − 2.4 × 10 −19 (Possible ecf)
work function energy = 2.7 × 10-19 (J)
C1
A1
[Total: 12]
14
2822/01
7
(a)
(b)
Mark Scheme
9
9
×
×
(Four correct: 3 marks, three correct: 2 marks, two correct: 1 mark)
λ=
h
mv
/λ =
h
p
(Any subject)
June 2006
B3
C1
6.63 × 10−34
v=
6.8 × 10−11 × 2.0 × 10− 26
speed = 490 (m s-1)
C1
A1
[Total: 6]
15