E.3.18 (HL)—Beta spectrum and neutrino

Read the beta spectrum

Beta particles from one radioactive transition are emitted with a continuous range of kinetic energies, from nearly zero up to a maximum.

Use energy sharing

The beta particle and neutrino share the decay energy in variable proportions. The neutrino therefore explains why the beta particle does not always receive one fixed energy.

Common trap

Do not attribute the continuous spectrum to a continuous set of nuclear levels. Alpha and gamma line spectra show the contrasting discrete-level behaviour.

How it is assessed

Questions identify the reason beta energy is continuous.

Command terms

Identify

What earns marks

Choose or state the existence of the neutrino, not gamma emission or continuous nuclear levels.

Watch for

Choosing gamma emission or nuclear energy levels as the explanation.

Retrieve the HL evidence

Nuclear stability, scattering deviations, the N–Z stability band and discrete alpha/gamma spectra reveal the strong interaction and quantized nuclear levels.

Retrieve the decay equations

Use $N=N_0e^{-\lambda t}$ , $A=\lambda N$ , and $T_{1/2}=\ln2/\lambda$ . The continuous beta spectrum is explained by neutrino energy sharing.

E.3.18 (HL)—Beta spectrum and neutrino

Explain Beta Spectrum

E.3.18 (HL) Exam Analysis

Assessment in practice

Retrieve the HL Nuclear Model