Energy of Alpha and Beta Particles in Decay (HBL 7/9/2026)

​ENERGY OF ALPHA AND BETA PARTICLES

PARTICLE PHYSICS AS & A LEVEL PHYSICS, STA HB

Multiple Choice

What quantity is used to identify an element?

• nucleon number

• proton number

• neutron number

• I don't know

Multiple Choice

Deuterium and Tritium are both isotopes of Hydrogen.

Which of the following statements are correct?

• they are different elements

• they have the same number of neutrons

• they have the same number of protons

• they have the same nucleon number

Multiple Select

What causes nuclei to be unstable and undergo decay process? Select all that apply.

• they have too much neutrons

• they have too much protons

• they have too much energy

• they have too much problem

Multiple Choice

What is an alpha particle?

• Helium gas

• Helium atom

• Helium nucleus

• Helium

Multiple Choice

What is the nature of a Beta minus particle?

• it is a proton

• it is an electron

• it is a positron

• it is a neutrino

Multiple Choice

In beta decay, apart from a beta particle, what else is emitted?

• alpha particle

• gamma ray

• neutrino

• electron

LESSON OUTCOMES

By the end of the lesson, you should be able to:

1. Analyse graphs of energy of emitted particles in a decay process to determine the type of decay

2. Describe that the energy of alpha particles as a result of radioactive decay is discrete

3. Describe that beta particles have a continuous range of energies in beta decay due to the emission of neutrinos and antineutrinos

KINETIC ENERGY OF PARTICLES EMITTED IN DECAY

LO: Analyse graphs of energy of emitted particles in a decay process to determine the type of decay

Open Ended

What feature of each graph is useful for identifying the type of decay?

Open Ended

Hence, what conclusion can you make regarding the energy of alpha and beta particles?

KINETIC ENERGY OF PARTICLES EMITTED IN DECAY

LO: Describe that the energy of alpha particles as a result of radioactive decay is discrete and that beta particles have a continuous range of energies in beta decay

DISCRETE CONTINUOUS RANGE

Open Ended

A graph of intensity against kinetic energy is shown. Identify and explain whether this is an alpha particle or a beta particle.

Open Ended

A graph of intensity against kinetic energy is shown. Identify and explain whether this is an alpha particle or a beta particle.

Open Ended

Based on the equations of alpha and beta decay, suggest a possible explanation to why beta particles have a continuous range of energy.

ENERGY OF ALPHA PARTICLES

LO: Describe that the energy of alpha particles as a result of radioactive decay is discrete and that beta particles have a continuous range of energies in beta decay

To conserve energy and momentum, energy is shared in specific portions between the daughter nucleus and the alpha particle.

ENERGY OF BETA PARTICLES

LO: Describe that the energy of alpha particles as a result of radioactive decay is discrete and that beta particles have a continuous range of energies in beta decay

Energy shared between daughter nucleus, beta particle, and neutrinos/antineutrinos.

The beta particle does not receive all the energy, but rather share it with the neutrinos

Poll

Would the neutrino disappear if the β particle had maximum energy?

• Yes

• No

Open Ended

If the beta particle receive less energy, where does the rest go?

LESSON OUTCOMES

By the end of the lesson, you should be able to:

1. Analyse graphs of energy of emitted particles in a decay process to determine the type of decay

2. Describe that the energy of alpha particles as a result of radioactive decay is discrete

3. Describe that beta particles have a continuous range of energies in beta decay due to the emission of neutrinos and antineutrinos

Open Ended

How would you explain the difference between α-particle and β-particle energies to a friend who was absent today?

Open Ended

If you were given an unknown energy spectrum tomorrow, what would you look for first to determine whether it represents α or β decay? Why?

2 more lessons before the finish line!

NEARING THE END

Let's reflect.

Poll

In the beginning of the year, what was your main reason for doing A Level Physics?

• I'm interested / like Physics

• It will help my future prospect (career/uni course)

• I have no other option

• Other

Poll

Since then, has anything change now?

• Yes - I am more interested

• Yes - I am less interested

• No - I still feel the same