Particle Physics

Question 1

What is concerved in a nuclear reaction?

Answer 1

Mass-Energy is conserved
Momentum is conserved
Electric charge is conserved

Question 2

Disintegration energy

Answer 2

The energy released when a radioactive disintegration takes place spontaneously.

Question 3

What is radioactive decay

Answer 3

Radioactive Decay is the disintegration of an unstable nucleus with the emission of one or more types of radiation.

Question 4

What is the structure of an alpha particle?

Answer 4

An alpha-particle is a helium nucleus, i.e. a bundle of two protons and two neutrons, emitted from the nucleus of a radioactive atom.

Question 5

Example of an alpha particle emitter

Answer 5

238
U is an alpha-particle emitter.
92

Question 6

What is the nature of a beta particle

Answer 6

A beta-particle is a high-speed electron emitted from the nucleus of a radioactive atom.

Question 7

Example of a beta particle emitte

Answer 7

14
Carbon-14. C
6

Question 8

Beta decay changes the values how?

Answer 8

When an electron or beta particle is emitted from an element, the atomic number increases by one and the mass number stays the same

Question 9

When a nucleus undergoes beta decay it appeared that
momentum was not conserved.
How did Fermi’s theory of radioactive decay resolve this?

Answer 9

It proposed the existence of another particle, called the neutrino, ν, that had the missing momentum.

Question 10

Who and when
Proposed the existence of the neutrino?
Detected it?

Answer 10

The existence of the Neutrino was proposed in 1930 by Wolfgang Pauli, but it was not detected until 1956 by Cowan and Reines.

Question 11

Give two reasons why it is difficult to detect a neutrino?

Answer 11

The Neutrino:
is uncharged
has a very small mass
& interacts weakly with matter.

Question 12

Each particle has its own anti-particle. What is an Anti-Particle?

Answer 12

The Anti-Particle of a given particle has the same mass as the given particle, and its charge is equal but with opposite sign

Question 13

Compare the properties of the Electron with those of its anti-particle, the Positron.

Answer 13

The electron and the positron have the same mass. The electron and positron have the same size electric
charge.
The electron has negative charge; the positron has positive charge.
An electron is matter; a positron is anti-matter. The electron and positron have opposite spin.

Question 14

What is anti-matter

Answer 14

Anti-Matter is material or matter made up of anti- particles of the particles out of which normal matter is made.
The anti-particles have the same mass and a charge of equal size but opposite sign to their corresponding particles.

Question 15

What is meant by pair production

Answer 15

Pair production is the creating of a particle and its anti- particle from electromagnetic energy (gamma rays).

Question 16

In an accelerator two protons are accelerated to very high speed (i.e. very high kinetic energy) and made to collide with each other.

What reaction occurs?

Answer 16

The kinetic energy of the protons is converted into matter in the form of other particles.

Question 17

In an accelerator two protons are accelerated to very high speed (i.e. very high kinetic energy) and made to collide with each other.

Write an equation showing this reaction.

Answer 17

p + p + energy → p + p + additional particles

Question 18

In an accelerator two protons are accelerated to very high speed (i.e. very high kinetic energy) and made to collide with each other.
What happens if the kinetic energy of the colliding protons is increased?

Answer 18

More particles and particles of greater masses are produced.

Question 19

Particles are classified according to whether they feel the Strong Nuclear Force or not. There are thus two families of particles. Name them.

Answer 19

The Leptons and the Hadrons.

Question 20

What is a Lepton?

Answer 20

A Lepton is an elementary particle that does not feel the Strong Nuclear Force.

A Lepton feels:
the Weak Nuclear Force,
the Gravitational Force
and if it is charged, the Electromagnetic Force.

Question 21

What is a Hadron?

Answer 21

A Hadron is a particle that does feel the Strong Nuclear Force.

A Hadron feels:
the Strong Nuclear Force the Weak Nuclear Force,
the Gravitational Force
and if it is charged the Electromagnetic Force.

Question 22

What is an Elementary Particle?

Answer 22

An Elementary Particle is a particle that is not made up of other particles and has no internal
structure.
Leptons are Elementary Particles.

Hadrons are not elementary particles.

Question 23

Hadrons are not elementary particles.

What are they made up of?

Answer 23

Hadrons are made up of elementary particles
called Quarks and Antiquarks.
Hadrons are divided into two families, called the Baryons and the Mesons.

Question 24

What are Mesons?

Answer 24

Mesons are hadrons that have masses between that of the electron and the proton.

Question 25

What are Baryons?

Answer 25

Baryons are hadrons that have masses greater than or equal to that of the proton.

Question 26

What are Quarks?

Answer 26

Quarks (and Anti-Quarks) are Elementary Particles out of which hadrons (i.e. baryons and mesons) are made.
Quarks have an electric charge of: +/- 1/3 e or +/- 2/3e

Question 27

Name the six flavours of quark?

Answer 27

Up, Down
Strange, Charmed
Top, Bottom

Question 28

What is the quark composition of a Baryon?

Answer 28

A Baryon is made up of any three quarks (or any three anti-quarks)

Question 29

What is the quark composition of a proton?

Answer 29

A proton consists of two up quarks and a down quark. Protons are baryons.

Question 30

What is the quark composition of a Meson?

Answer 30

A Meson is made up of any one quark and any one anti-quark

Question 31

Name three negatively charged quarks and their charges.

Answer 31

Down. -1/3e
Strange -1/3e
Bottom. -1/3e

Question 32

Name three positively charged particles and their charge

Answer 32

Up. +2/3 e
Charmed +2/3 e
Top. +2/3 e