particle physics

Question 1

beta minus decay

Answer 1

n protons increase

Question 2

when describing decay process (3)

Answer 2

• name decay
• how does nucleon n change
• how does atomic number change

Question 3

(2) why alpha radiation not pose any risk in the smoke detector

Answer 3

(1) only small quantity needed (highly ionising and long half-life
(1) particles do not travel more than a few cm’s (penetrating ability)

Question 4

what is ionisation ?

Answer 4

Ionisation is the removal (or addition) of electrons from (to) an atom or molecule

Question 5

why leptons cannot decay further

Answer 5

stable (fundamental)

Question 6

explain why when UV shone on positiviley charged plate no charge is lost

Answer 6

process involved the ejection of electrons(1)

which only make it more positive(1)

Question 7

2 differences exchange particle weak + strong

Answer 7

gluons lighter bosons more massive (1)

gluons have longer range bosons have shorter range (1)

Question 8

explain what is meant by an exchange particle (2)

Answer 8

moves between one object and another/carrier acting
on two particles
gives rise to the force between the particles

     gluon(s) (accept pions

Question 9

The deuterium nucleus is stable.
Describe how the variation of the strong nuclear force with distance contributes to the
stability of the deuterium nucleus.
[3 marks]

Answer 9

(Short-range) attraction up to about 3 fm  (Very short-range) repulsion closer than 0.5 fm 
Prevent proton and neutron moving closer or further apart 

Question 10

exchange particle of strong nuclear force

Answer 10

pion/gluon

Question 11

Tritium is an isotope of hydrogen. Its nucleus contains one proton and two neutrons. Tritium undergoes radioactive decay.
Three modes of radioactive decay are
• alpha decay −
• beta minus (β ) decay • electron capture.
Deduce which of these modes could produce the nucleus of another element when
the tritium nucleus decays.
[3 marks]

Answer 11

Correct description of alpha decay
OR
Consequence of alpha decay
Correct description of electron capture
OR
Consequence of electron capture
Correct description of beta decay, with explicit conclusion that this mode is valid

Question 12

whats released in annihilation

Answer 12

photon(s) of !electromagnetic radiation!

Question 13

why mass is not always conserved

Answer 13

mass can be converted to energy and vice versa

Question 14

In the strong interaction,
K– + p → K0 + K+ + X,
deduce the quark composition of, and state the type of, hadron represented by X.

Answer 14

X = sss (1) (= Ω–)

baryon (1)

Question 15

A positive muon may decay to a positron and two neutrinos. Write down an equation representing the muon decay.
μ+ →

Answer 15

μ+ → e+ + ve + (+Q)

Question 16

instead of saying escape metal say

Answer 16

overcome work function

Question 17

what is meant by threshold frequency

Answer 17

• below a certain frequency no electrons emitted

- minimum frequency for electrons to overcome work function

Question 18

why the photoelectric effect is not observed below a certain frequency? (3)

Answer 18

• energy photon depends on the frequency (1)
• below threshold frequency photon does not have enough energy to liberate electron (1)
• photon does not have enough energy to overcome work function

Question 19

what’s threshold freq?

Answer 19

minimum energy required for electron to escape surface of metal

Question 20

ionisation energy

Answer 20

energy to remove electron from ground state

Question 21

explain process pair production (3)

Answer 21

photon interacts w/ orbital electron
energy photon creates particle anti particle pair
to conserve momentum photon interacts w/ intracting particle

Question 22

calculate max frequency photons in annihilation 2 points

Answer 22

freq of one photon

mark scheme says must show explaining how it’s two

Question 23

role exchange particles in exchange forces between particles (1)

Answer 23

forces arise when exchange particles move between other particles

Question 24

a discussion of the stability of free hadrons

- what is most stable baryon

Answer 24

proton

Question 25

a discussion of the stability of free hadrons.]

mesons

Answer 25

• kaon decay into pions

Question 26

is X and Y same charge but X greater mass determine nuclear compositions diff

Answer 26

same number protons but X has more neutrons

Question 27

when would weak nuclear force be responsible for something

Answer 27

• change in quark type

- involved leptons AND hadrons

Question 28

weak nuclear force changes quarks by

Answer 28

By emitting an electrically charged W boson, the weak force changes the flavor of a quark, which causes a proton to change into a neutron, or vice versa.

Question 29

if leptons involved

Answer 29

can’t be strong nuclear force

Question 30

3 marker on how you can find interaction from resulting nucleus

Answer 30

go through equation and what is released / found

Question 31

why is it important for many diff ppl to take part in advances in particle physics

Answer 31

peer review
expensive (e.g. particle accelerator)
-many skills + disciplines needed

Question 32

for antiparticle definition

Answer 32

all properties opposite but mass number same

Question 33

don’t say mass say

Answer 33

rest mass

Question 34

baryon number of anti proton is

Answer 34

-1

Question 35

photon anti particle

Answer 35

it’s its own anti particle

Question 36

4 marker on how force works use EM and photon

Answer 36

• EM
• photon
• trasnfer energy/momentum
• particle receives exchange particle new particle creation occurs

Question 37

Ko made out of what

Answer 37

down anti strange

Question 38

on anti particle of electron say

Answer 38

positron (DO NOT ACCEPT ANTI ELECTRON)