Radioactivity

Question 1

Typical Nuclear sizes

Answer 1

1fm

Question 2

Radioactive Decay

definition

Answer 2

Spontaneous emission of radiation that changes state of the nucleus

Question 3

What is alpha Decay

Answer 3

The helium nucleus is emitted from the parent nucleus.
Strongly ionising, heavy, charge of 2e. Damaging in the body

Question 4

What is Beta Decay

Answer 4

High energy electron or positron is emitted from nucleus.

Less ioinsing than alpha but faster and lower charge

Question 5

Beta plus deacy

Answer 5

proton -> neuton + neutrino + positron

Question 6

Beta minus decay

Answer 6

neutron -> proton + antineutrino + electron

Question 7

What is Gamma Decay?

Answer 7

nucleus de-excites and emits gamma ray photons. Very energetic, weakly ionoising and uncharged

Question 8

Activity definition

Answer 8

Number of decays per second

Question 9

Mean lifetime in radioactive decay

equation

Answer 9

τ =
integral (t|dN/dt|) dt
/
integral (|dN/dt| )dt
.

Question 10

Activity at which decay occurs equation

Answer 10

A = λN

Question 11

What decay processes unstable nucleus

Answer 11

Alpha and Beta decay

Question 12

What decay changes nuclear species

Answer 12

gamma decay

Question 13

Energy Release equation

Answer 13

Q =
[(Sum of nuclear masses of reactants) −
(Sum of nuclear masses of products)]c^2

Question 14

What is required for a decay to be energetically possible?

Answer 14

Q>0

Question 15

What decay is more significant for heavier nuclei and what is it caused by

Answer 15

Alpha emission - Coulomb Repulsion effect
As Coulomb effect increases with Z^2 and nuclear binding force increases with A

Question 16

Nuclear Mass conversion equation

Answer 16

Nuclear mass = Atomic MASS - Z(Mass of electrons)

Question 17

What is the Geiger Nuttall Rule

Answer 17

Relates energies of emitted alpha particle and half-lives of nuclides.

• Alpha particle is pre-formed in nucleus
• Alpha particle moves in spherical pot well created by daughter nucleus.
• Alpha particle has energy equal to Q as most energy release is carried by particle

Question 18

What are the three regions of interest in the Geiger Nuttall Rule?

Answer 18

where r represents the distance between the α particle and daughter
nucleus.

1 - r<a; potential well has depth of -v0. Particle is classically confined.

2 - outside r<a repulsive coulomb potential present w cut off at r=a. For a < r < b, there is a barrier region, where the potential energy is greater than
Q

3 - 3. The region r > b is classically permitted outside the barrier.