What did Rutherford's alpha-particle scattering experiment reveal about the atom?

It showed that atoms are mostly empty space, with nearly all their mass and positive charge concentrated in a tiny, dense nucleus.

How do you calculate the initial number of radioactive nuclei from activity and decay constant?

Use A = λN, so N = A/λ. For 3.5 × 10^10 Bq and 0.15 s^-1, the initial number is about 2.3 × 10^11 nuclei.

What do control rods do in a nuclear reactor?

They absorb neutrons to control the rate of the fission chain reaction; inserting them further reduces or stops the reaction.

Free Course Image Nuclear Physics and Radioactivity

Free online course Nuclear Physics and Radioactivity

Duration of the online course: 1 hours and 24 minutes

New

Master nuclear physics for exams: decay, half-life, fission and fusion with a free online course and practice questions to sharpen your calculations fast.

In this free course, learn about

Structure of the nucleus: nucleons, isotopes, nuclear size and density
Strong nuclear force and quark model basics (protons/neutrons made of quarks)
Rutherford alpha-scattering conclusion: tiny, dense, positively charged nucleus
Radioactive decay quantities: activity, decay constant, and half-life
Using N(t)=N0 e^(-λt) and A=λN to find particle number from activity
Beta decay mechanism and nuclear equations (including neutrino/antineutrino)
Binding energy and mass defect; reading/using binding energy per nucleon graphs
Energy release (Q-value) in nuclear reactions using mass-energy equivalence
Nuclear fission vs fusion: conditions, products, and why energy is released
Nuclear reactors: chain reactions, criticality, and how control rods regulate rate

About the free online course

Build confidence in nuclear physics and radioactivity with a focused, exam-ready learning experience designed for school-level Physics. This course helps you move from memorizing facts to understanding how nuclear models explain real observations, so you can tackle typical assessment questions with clarity and speed. You will revisit the structure of the atom, why the nucleus is stable despite strong electrostatic repulsion, and how experimental evidence shaped the modern picture of nuclear size and charge distribution.

Radioactivity is treated as a topic you can calculate with, not just describe. You will learn to connect activity, decay constant, and number of unstable nuclei, and to interpret exponential decay in a way that makes half-life problems feel intuitive. Along the way, you will strengthen your ability to handle scientific notation, units, and rearranging key equations without losing physical meaning. Practice questions are integrated to help you spot common traps and improve accuracy under time pressure.

The course also develops a clear qualitative and quantitative sense of nuclear energy. You will work with binding energy ideas to explain why some reactions release vast amounts of energy, and how fission and fusion differ in mechanism and outcomes. Realistic examples reinforce how mass-energy changes are linked to nuclear stability, and why certain decay pathways are more likely than others.

Finally, you will connect theory to applications through nuclear reactors, including how reaction rates are managed for safe, steady power output. By the end, you should be able to explain key nuclear concepts in clean Physics language and solve core calculation problems with greater confidence, whether you are revising for exams or strengthening fundamentals for the next level of study.

Course content

Video class: A Level Physics Revision: All of Nuclear Physics - the nucleus, strong force, quarks, beta decay 23m
Exercise: What was the main conclusion from Rutherford's alpha particle scattering experiment about the nucleus?
Video class: A Level Physics Revision: Radioactivity - activity, the decay constant and exponential decay 07m
Exercise: What is the initial number of particles for a source with activity of 3.5 x 10^10 Bq and decay constant 0.15 s^-1?
Video class: A Level Physics Revision: Nuclear Physics, Binding Energy, Fission and Fusion 20m
Exercise: What is the energy released during the nuclear reaction of carbon-14 to nitrogen-14 via beta decay?

Video class: NUCLEAR Physics and Radioactivity REVISION questions 33m
Exercise: What is the role of control rods in nuclear reactors?

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