A2 Physics
P24 

	

	Name:	
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Class:	
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Date:	
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Chapter 24. Particle physics	
Exam style questions 	

Q1.
What is the best estimate for the order of magnitude for the diameter of an atom?
 
A	10−14 m		
B	10−12 m		
C	10−10 m		
D	10−8 m		
(Total 1 mark)
Q2.
When bombarded with an α particle the nuclide  changes into another nuclide with the emission of a neutron and γ radiation.
What are the correct values for the nucleon number and proton number of the nuclide which is formed?
 
 	Nucleon number	Proton number	 	
A	29	14		
B	29	12		
C	28	14		
D	27	12		
(Total 1 mark)
Q3.
 
An α particle travels towards a gold nucleus and at P reverses its direction.
Which one of the following statements is incorrect?
A       The electric potential energy of the α particle is a maximum at P.
B       The kinetic energy of the α particle is a minimum at P.
C       The total energy of the α particle is zero.
D       The total energy of the α particle has a constant positive value.
(Total 1 mark)
Q4.
An α particle makes a head−on collision with a gold nucleus containing 79 protons. The distance of closest approach of the α particle to the nucleus is 4.0 × 10−14 m.
What electrostatic force acts on the gold nucleus when at this separation?
 
A	9.1 × 10−11 N		
B	23 N		
C	290 N		
D	1.4 × 1020 N		
(Total 1 mark)
Q5.
An α particle with an initial kinetic energy of 4.9 MeV is directed towards the centre of a gold nucleus of radius R which contains 79 protons. The α particle is brought to rest at point S, a distance r from the centre of the nucleus as shown in the diagram below.
 
(a)     Calculate the electric potential energy, in J, of the α particle at point S.
electric potential energy = ___________________ J
(2)
(b)     Calculate r, the distance of closest approach of the α particle to the nucleus.

r = ___________________ m
(3)
(c)     Determine the number of nucleons in the gold nucleus.
R, radius of the gold nucleus = 7.16 × 10−15 m
r0 = 1.23 × 10−15 m
number of nucleons = ________________
(3)
(d)     The target nucleus is changed to one that has fewer protons. The α particle is given the same initial kinetic energy.
Explain, without further calculation, any changes that occur to the distance r. Ignore any recoil effects.
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
(2)
(Total 10 marks)
Q6.
The radius of a nucleus of the iron nuclide  is 4.35 × 10–15 m.
What is the radius of a nucleus of the uranium nuclide ?
 
A	2.69 × 10–15 m		
B	2.89 × 10–15 m		
C	6.55 × 10–15 m		
D	7.05 × 10–15 m		
(Total 1 mark)

Q7.
An electron collides with a neutral atom and ionizes it. Which of the following describes the particles present after the collision?
 
A	An electron and an excited atom.		
B	An excited atom containing an excess electron.		
C	Two electrons and a positive ion.		
D	Two electrons and a neutral atom in the ground state.		
(Total 1 mark)
Q8.
A positive ion has a charge−to−mass ratio of 2.40 × 107 C kg–1. It is held stationary in a vertical electric field.
Which line, A to D, in the table shows correctly both the strength and the direction of the electric field?
 
 	Electric field strength / V m–1	Direction	
A	4.09 × 10–7	upwards	
B	4.09 × 10–7	downwards	
C	2.35 × 106	upwards	
D	2.35 × 106	downwards	
(Total 1 mark)
Q9.
Which equation shows the process of annihilation?
 
A	π− + π → γ		
B			
C	β− + p → γ		
D	γ + γ → β+ + β−		
(Total 1 mark)

Q10
(a)     Pair production can occur when a photon interacts with matter. Explain the process of pair production.
___________________________________________________________________
___________________________________________________________________
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___________________________________________________________________
(2)
(b)     Explain why pair production cannot take place if the frequency of the photon is below a certain value.
___________________________________________________________________
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(3)
(c)     Energy and momentum are conserved during pair production. State two other quantities that must also be conserved.
___________________________________________________________________
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(2)
(Total 7 marks)

Q11.
Under certain circumstances it is possible for a photon to be converted into an electron and a positron.
(a)     State what this process is called.
___________________________________________________________________
(1)
(b)     A photon must have a minimum energy in order to create an electron and a positron.
Calculate the minimum energy of the photon in joules. Give your answer to an appropriate number of significant figures.

 
 
minimum energy = ____________________ J
(3)
(c)     A photon of slightly higher energy than that calculated in part (b) is converted into an electron and a positron.
State what happens to the excess energy.
___________________________________________________________________
___________________________________________________________________
(1)
(d)     Describe what is likely to happen to the positron shortly after its creation.
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
(2)
(Total 7 marks)
Q12.
Under certain circumstances, a photon moving through a material can interact with the nucleus of an atom of the material to produce an electron and a positron.
(i)      What is the name of this process?
___________________________________________________________________
(1)
(ii)      Give one reason why the photon could not produce a single electron instead of an electron and a positron.
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
(2)
(iii)     Make use of the Data and Formulae booklet to show that the minimum energy of the photon required for this process is 1.02 MeV.

 
 
(1)
(iv)     Photons whose wavelength exceeds a certain value will not cause this process.
Calculate the maximum wavelength for the process to occur stating your answer to an appropriate number of significant figures.

 
 
answer = ______________________ m
(4)
Q13.
Under certain conditions a photon may be converted into an electron and a positron.
(a)     State the name of this process.
___________________________________________________________________
(1)
(b)     For the conversion to take place the photon has to have an energy equal to or greater than a certain minimum energy.
(i)      Explain why there is a minimum energy.
______________________________________________________________
______________________________________________________________
(2)
(ii)     Show that this minimum energy is about 1 MeV.
 
(1)
(iii)     Explain what happens to the excess energy when the photon energy is greater than the minimum energy.
______________________________________________________________
______________________________________________________________
(1)
(iv)     A photon has an energy of 1.0 MeV.
Calculate the frequency associated with this photon energy.
frequency = __________ unit = __________
(4)
(Total 9 marks)
Q14.
Cosmic rays are high-energy particles coming from Space. They collide with the air molecules in the Earth’s atmosphere to produce pions and kaons.
(a)     Pions and kaons are mesons. Identify the quark–antiquark composition for a meson. (1)

qqq	 	
qq̄q̄	 	
qq̄	 	
qq	 	
 (b)     A positron with a kinetic energy of 2.0 keV collides with an electron at rest, creating two photons that have equal energy.
Show that the energy of each photon is 8.2 × 10−14 J

(3)
(c)     Calculate the wavelength of a photon of energy 8.2 × 10−14 J.
wavelength = _______________________ m
(2)
(d)     Show that the speed of the positron before the collision was about 2.7 × 107 m s−1.
(3)
(e)     Calculate the de Broglie wavelength of the positron travelling at a speed of
2.7 × 107 m s−1.
wavelength = _______________________ m
(2)
(f)     The separation between the carbon atoms in graphite is about 0.15 nm.
Discuss whether electrons travelling at 2.7 × 107 m s−1 can be can be used to demonstrate diffraction as they pass through a sample of graphite.

___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
(4)
(Total 15 marks)
Q15.
What of the following is a hadron of zero charge?					(Total 1 mark)

A	neutrino		
B	photon		
C	proton		
D	neutron		
Q16.
What is the quark structure for antiprotons?						(Total 1 mark)

A			
B			
C			
D			
Q17.
Which of the following is not true?						(Total 1 mark)

A	Each meson consists of a single quark and a single antiquark.		
B	Each baryon consists of three quarks.		
C	The magnitude of the charge on every quark is  		
D	A particle consisting of a single quark has not been observed.		

Q18.
(a)     Give the name of a particle that is a hadron.
___________________________________________________________________
(1)
(b)     Pions are mesons. Give a possible quark structure for a pion.
___________________________________________________________________
(1)
(Total 2 marks)
Q19.
Which line correctly classifies the particle shown?					(Total 1 mark)

 	Particle	Category	Quark combination	 	
A	neutron	baryon	ūd		
B	neutron	meson	udd		
C	proton	baryon	uud		
D	positive pion	meson	ūd		
Q20.
What are the numbers of hadrons, baryons and mesons in an atom of 7 3Li?  (Total 1 mark)
  
 	hadrons	baryons	mesons		
A	7	3	3		
B	7	4	4		
C	7	7	0		
D	10	7	0		
Q21.
(a)     Complete the table by naming one example of each type of particle.		(3)

type of particle	example	
lepton	 	
baryon	 	
meson	 	
 (b)     The following reaction cannot occur.
π+ + n → p + π–
(i)      State and explain which conservation law would be broken by this reaction. 	 (2)

______________________________________________________________
______________________________________________________________
____________________________________________________________
 (ii)     State and explain one conservation law that would not be broken in this reaction.
______________________________________________________________
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______________________________________________________________
(1)
(c)     Describe what happens when a proton and an antiproton collide.
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(2)
(Total 8 marks)
Q22.
(a)     (i)      Name two baryons.
______________________________________________________________
(2)
(ii)     State the quark structure of the pion .
______________________________________________________________
(1)
(b)     (i)      The K+ kaon is a strange particle. Give one characteristic of a strange particle that makes it different from a particle that is not strange.
______________________________________________________________
______________________________________________________________
(1)
(ii)     One of the following equations represent a possible decay of the K+ kaon.
K+ → π+ + π0
K+→ μ+ + 
State, with a reason, which one of these decays is not possible.
______________________________________________________________
______________________________________________________________
(2)
(c)     Another strange particle, X, decays in the following way:
X → π– + p
(i)      State what interaction is involved in this decay.
______________________________________________________________
(1)
(ii)     Show that X must be a neutral particle.
______________________________________________________________
______________________________________________________________
(1)
(iii)     Deduce whether X is a meson, baryon or lepton, explaining how you arrive at your answer.
______________________________________________________________
______________________________________________________________
______________________________________________________________
______________________________________________________________
(2)
(iv)    Which particle in this interaction is the most stable?
______________________________________________________________
(1)
(Total 11 marks)
Q23.
(a)     Hadrons are a group of particles composed of quarks. Hadrons can either be baryons or mesons.
(i)      What property defines a hadron?
______________________________________________________________
(1)

(ii)     What is the quark structure of a baryon?
______________________________________________________________
(1)
(iii)     What is the quark structure of a meson?
______________________________________________________________
(1)
(b)     State one similarity and one difference between a particle and its antiparticle.	(2)

similarity ___________________________________________________________
___________________________________________________________________
difference ___________________________________________________________
___________________________________________________________________
 (c)     Complete the table below which lists properties of the antiproton.
 
 	charge / C	baryon number	quark structure	
antiproton	 	 	 	
 (d)     The K– is an example of a meson with strangeness –1. The K– decays in the following way:										(2)
K– → µ– + 
(i)      State, with a reason, what interaction is responsible for this decay.      	(2)
	
______________________________________________________________
______________________________________________________________
______________________________________________________________
 (ii)     State two properties, other than energy and momentum, that are conserved in this decay. (2)

______________________________________________________________
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(v)     Explain what will happen to the positron produced by the interaction.
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(2)
(Total 10 marks)
Q24.
Which statement concerning the forces between particles is incorrect?
 
A	Leptons experience the weak interaction.		
B	Leptons experience the strong interaction.		
C	Hadrons experience the weak interaction.		
D	Hadrons experience the strong interaction.		
(Total 1 mark)

Q25.
Which row shows the correct interactions experienced by a hadron or a lepton?
 
 	Particle	Strong interaction	Weak interaction	 	
A	Hadron	Yes	Yes		
B	Lepton	Yes	Yes		
C	Hadron	Yes	No		
D	Lepton	Yes	No		
(Total 1 mark)
Q26.
The composition of a carbon dioxide (CO2) molecule is one atom of  and two atoms of .
What is the number of molecules of CO2 in 2.2 kg of the gas?
 
A	1.0 × 1022		
B	3.0 × 1022		
C	3.0 × 1025		
D	4.7 × 1025		
(Total 1 mark
Mark schemes
Q1.
C
[1]
Q2.
C
[1]
Q3.
C
[1]
Q4.
B
[1]
Q5.
(a)     1eV = 1.6 × 10−19 J
kinetic energy = 1.6 × 10−19 × 4.9 × 106 = 7.8(4) × 10−13 J ✔
ke lost = pe gained = 7.8(4) × 10−13 J ✔
2
(b)     using V = Q / 4πεor and Ep = qV
r = qQ/4πεoEp✔
= (2 × 1.6 × 10−19) (79 × 1.6 × 10−19)/4π × 8.85 × 10−12 × 7.84 × 10−13✔
r = 4.67(4.64) × 10−14 m ✔
3
(c)     A = (R/r0)3 ✔
= (7.16 × 10−15 / 1.23 × 10−15 m)3 ✔
= 197 placed on the dotted line ✔
3
(d)     r gets smaller ✔
less force so needs to travel further to lose same initial ke ✔
Fewer protons means that r will be smaller when alpha particle has the same electrostatic potential energy (as initial kinetic energy)	2       [10]	
Q6.
D
[1]
Q7.
C
[1]
Q8.
A
[1]
Q9.
B
[1]
Q10.
(a)    photon interacts with (orbital) electron/nucleus/atom   
energy of photon used to create particle antiparticle pair  
to conserve momentum photon needs to interact with interacting particle  
2
(b)     energy of photon depends on frequency  
if energy/frequency is below a certain value there is not enough energy  
to provide mass/rest energy of particles  
3
(c)     any two   
eg charge
lepton number
baryon number
strangeness
2
[7]

Q11.
(a)    pair production  
1
(b)     (energy = 2 × rest mass energy)
energy = 2 × 0.510999 = 1.021998 (MeV) 
energy = 1.021998 × 1.60 × 10−13 = 1.64 × 10−13 J 
(3 sig figs )
If miss out 2 factor can get CE
Can use E=2mc2
First mark for full substitution and second mark for answer
3
(c)     kinetic energy (of electron and positron)  
KE of photon gets zero
1
(d)     (meet an electron and) annihilate 
(converting into two or more) photons  OR gamma rays
2
[7]
Q12.
(i)      pair production (1)
1
(ii)      conservation law stated (charge or lepton number) (1)
shown to be true eg lepton number +1–1 = 0 (1)
2
(iii)     energy = 2 × 0.510 (ignore sfs) (1)
1
(iv)     E = (1.02 × 1.6 × 10–13) = 1.63 × 10–13 (1)
1.63 × 10–3 = 6.63 × 10–34 × 3.00 × 108/λ (1)
λ = 6.63 × 10–34 × 3.00 × 108/1.63 × 10–13 = 1.22 × 10–12 m (1)
3 significant figures (1)
4
(v)     will encounter an electron and the two particles will annihilate (1)
releasing (two high energy/gamma) photons/quanta (1)
2
[10

Q13.
(a)     pair production ✔
1
(b)     (i)      energy of photon needs to provide
at least the rest masses ✔
OR at least the rest energy ✔
of the electron and positron / of (both) particles / of particle and antiparticle ✔
Of the electron and positron / of (both) particles of particle and antiparticle ✔
Can't score 2nd mark without having scored 1st
(allow particles or products)
TO on any suggestion of particles have KE
2
(ii)     minimum energy = 2 × 0.510999 = 1.021998 (MeV) ✔
must see working
and final answer must be at least 3 sf
allow detailed argument in reverse
0.5 Mev close to 0.511 MeV
Or E=mc2 leading to 1.024875 MeV
Or 2 × 5.5 × 10-4 × 931.5 = 1.02 MeV
1
(iii)     (electron / positron have) kinetic energy ✔
thermal energy n/e
Momentum n/e
1
(iv)     (attempts to convert energy to joules)
energy = 1.0 × 106 × 1.60 × 10-19 = 1.6 × 10-13 (J) ✔ 
Condone power 10 error on MeV
conversion to J
(use of E = hf)
Their energy ÷ 6.63 × 10-34 = f ✔
Must see subject or their f on answer line consistent with working
f = 2.4 × 1020 ✔ cao
Hz (condone s-1) ✔
Capital H and lower case z (for symbol)
Allow word written as Hertz (h lower case)
4
[9]

Q14.
(a)     qq̄✔
1
(b)     Total energy = 2keV + 2 × 511 keV = 1024 keV✔
= 1024 × 1.6 × 10−19 = 1.64 × 10−13J✔
Energy of each photon = 1.64 × 10−13/2 = 8.19 × 10−14 (J) ✔
First mark for calculating the total energy in keV.
Second mark is for converting correctly into joules.
Third mark is for dividing by two so ecf for incorrect conversion into joules. Student must show at least 3sf.
3
(c)     ✔    = 2.43 × 10−12 (m) ✔
First mark for the correctly rearranged equation or correct values substituted into equation.
Correct answer only scores 2 marks, ecf from 1 (b)
2
(d)     Ek= 2 keV = 2000 × 1.6 × 10−19 J = 3.2 × 10−16J✔
✔		= 2.65 × 107(m s−1) ✔
First mark for converting KE into joules.
Second mark for rearranging equation correctly or substituting correct values into equation.
Third mark for correct answer, must be to at least 3sf.
3
(e)     ✔	= 2.75 × 10−11(m) ✔
First mark for rearranging equation correctly or substituting correct values into equation.
Second mark for correct answer.
2
(f)     Recognition that separation is 1.5 × 10−10 m and compared to 0.28 × 10−10 (ecf)✔
wavelength is about 5 times less than gap width✔
 ✔
yes (diffraction would be observable)✔
Or words to that effect
4
[15]
Q15.
D
[1]
Q16.
D
[1]
Q17.
C
[1]
Q18.
(a)     one named hadron or obvious symbol						1
(b)     d/u/u/u or words						  		1   [2]
Q19.
C
[1]
Q20.
C
[1]
Q21.
(a)     electron/neutrino/tau/muon
          proton/neutron
          kaon/k particle/k meson/pion/pi meson
3
(b)     (i)      charge
         correct equation: 1 + 0 ≠ 1 + (–1)
1 mark lost for additional conservation law stated as broken
2
(ii)     any other correct conservation (lepton: 0 + 0 = 0 + 0;
baryon: 0 + 1 = 1 + 0; strangeness: 0 + 0 = 0 + 0)
1
(c)     annihilation
          release of energy/pair of gamma ray
2
[8]
Q22.
(a)     (i)      any two eg proton, neutron  
2
(ii)       
1
(b)     (i)      contains a strange quark
or longer half life than expected
or decays by weak interaction  
1
(ii)     the second one is not possible  
because lepton number is not conserved  
2
(c)     (i)      weak (interaction)  
1
(ii)     mention of charge conservation
or charge conservation demonstrated by numbers  
1
(iii)     X must be a baryon  
baryon number on right hand side is +1  
2
(iv)    proton/p  
1
[11]
Q23.
(a)     (i)      particles that experience the strong (nuclear) force/interaction (1)
1
(ii)     particles composed of three quarks (1)
1
(iii)     particles composed of a quark and an antiquark (1)
1
(b)     similarity:    but the same (rest) mass or rest energy (1)
difference:  opposite quantum states eg charge (1)
2

(c)     
 
 	charge/C	baryon number	quark structure	
antiproton	–1.6 × 10–19	–1	 	
–1 for each error								2
(d)     (i)      weak interaction (1)
strange not conserved or there is a change/decay of quark (flavour) (1)
2
(ii)     any two
eg charge
baryon number
(muon) lepton number
2
[11]
Q24.
B
[1]
Q25.
A
[1]
Q26.
C
[1]