7. Nuclear Properties

Question 1

Who invented the Plum Pudding Model?

Answer 1

JJ Thompson

Question 2

Describe the plum pudding model

Answer 2

Tiny negatively charged electrons are spread through the atom, which must be positively charged since overall the atom is neutral. The atom is seen as a positively charged diffuse sphere of matter with electrons embedded in it.

Question 3

Who first carried out Rutherford scattering?

Answer 3

Geiger and Marsden under Rutherford

Question 4

Describe the process of Rutherford scattering

Answer 4

Alpha particles were fired at gold film. It was found that a small number of particles underwent large scattering angles (which is very unlikely in the plum pudding model).

Question 5

What did Rutherford propose for the structure of the atom?

Answer 5

The planetary model of the atom. He proposed that atoms have a small positively charged core which contain most of the atomic mass.

Question 6

Rutherford scattering is often regarded as the _____ __ ________ ________.

Answer 6

Birth of nuclear physics.

Question 7

What assumptions are required to calculate the Rutherford cross section?

Answer 7

• There is a Coulomb interaction between the alpha particle and the nucleus.
• Scattering is elastic.
• The target is thin enough to only consider single scattering.

Question 8

What is the electric charge of a proton?

Answer 8

+1e

Question 9

What is the mass of a proton?

Answer 9

1.6726 x 10^-27 kg (0.9383 GeV/c^2)

Question 10

What is the spin of a proton?

Answer 10

1/2

Question 11

What is the electric charge of a neutron?

Answer 11

0

Question 12

What is the mass of a neutron?

Answer 12

1.6749 x 10^-27 kg (0.9383 GeV/c^2)

Question 13

What is the spin of a neutron?

Answer 13

1/2

Question 14

What is the parity operation?

Answer 14

An operator that reflects all spatial coordinates through the origin.

Question 15

A physical property has _____ parity if it is invariant under the parity operation.

Answer 15

Even

Question 16

A physical property has ____ parity if it changes sign under the parity operation.

Answer 16

Odd

Question 17

Does a scalar property like temperature have odd or even parity?

Answer 17

Even: scalar quantities have no direction so are not impacted by the parity operation.

Question 18

Does a vector property like velocity have odd or even parity?

Answer 18

Odd

Question 19

Describe the signs of a wave function with even parity

Answer 19

Question 20

Describe the signs of a wave function with odd parity

Answer 20

Question 21

What determines whether or not a wavefunction has odd or even parity?

Answer 21

Whether or not it is symmetric

Question 22

State the parity operator

Answer 22

Question 23

Parity is ______ for particles because they are said to have ‘__________’ parity, so are either odd (-) or even (+).

Answer 23

Fixed
Intrinsic

Question 24

Particles with half-integer spins (fermions) have ________ parity to their anti-particles.

Answer 24

Opposite

Question 25

Particles with integer spins (bosons) have ___ _____ parity to their anti-particles.

Answer 25

The same

Question 26

The parity of two or more particles (a composite system) is given by the algebraic product of the ___________ _________ and an __________ _________ _____.

Answer 26

Individual parities Angular momentum term

Question 27

Give the equation for the parity of 2 or more particles

Answer 27

P1, P2 = intrinsic parities l = angular momentum

Question 28

Which two forces do not violate parity?

Answer 28

- Strong nuclear force - Electromagnetic interactions

Question 29

Which force does violate parity?

Answer 29

- Weak nuclear force (which involves beta decay)

Question 30

Why does beta emission violate parity?

Answer 30

Because a beta emission is preferentially in the direction opposite the nuclear spin.

Question 31

Give the classical equation for magnetic moment

Answer 31

µ = magnetic moment e = electron charge r = radius v = speed m = electron mass l = angular momentum

Question 32

Give the quantum equation for magnetic moment

Answer 32

µ = magnetic moment e = electron charge m = electron mass l = angular momentum

Question 33

What is the Bohr magneton?

Answer 33

µ_B = Bohr magneton e = electron charge m_e = electron mass

Question 34

What is the nuclear magneton?

Answer 34

µ_N = nuclear magneton e = electron charge m_p = proton mass

Question 35

What is the magnetic moment for protons and neutrons? (In terms of angular momentum)

Answer 35

µ = magnetic moment g_l = orbital angular momentum g-factor (=1 for protons and =0 for neutrons) l = angular momentum µ_N = nuclear magneton

Question 36

Protons and neutrons have _________ _____ which also includes a magnetic moment.

Answer 36

Intrinsic spin

Question 37

What is the magnetic moment for protons and neutrons? (In terms of spin)

Answer 37

µ = magnetic moment g_s = spin g-factor s = spin (=1/2 for protons and neutrons) µ_N = nuclear magneton

Question 38

What is the EXPECTED spin g-factor for protons and neutrons?

Answer 38

Neutrons: zero Protons (and other spin 1/2 point particles): 2

Question 39

What is the spin g-factor for electrons?

Answer 39

-2.0023193043

Question 40

What is the spin g-factor for protons?

Answer 40

5.5856912

Question 41

What is the spin g-factor for neutrons?

Answer 41

-3.8260837

Question 42

What parity do protons have?

Answer 42

Even

Question 43

What parity do neutrons have?

Answer 43

Even

Question 44

Is a proton stable or unstable?

Answer 44

Very stable

Question 45

Is a free neutron stable or unstable?

Answer 45

Unstable

Question 46

Is the observed g-factor the same as expected for point particles?

Answer 46

No