Waves and Radiation is one of the three main areas in the National 5 Physics course and it regularly appears in exams. This unit covers everything from sound waves and light to the electromagnetic spectrum and nuclear radiation. Understanding these topics is key to picking up marks quickly. In this guide, we’ll break the unit into manageable chunks, highlight common exam questions, and give you clear revision tips.
If you’d like extra help, our SQA-experienced Physics tutors can build a study plan around your prelims or the final exam.
1) What are waves in Physics?
In Physics, a wave is a way of transferring energy from one place to another without transferring matter. This means the medium (such as air, water, or a solid) vibrates or oscillates, but the particles themselves don’t travel with the wave, only the energy does.
At National 5 you need to know the two main types of waves:
- Transverse waves – the particles vibrate at right angles to the direction the wave travels. Examples include water waves, light, and all electromagnetic (EM) waves. When you draw them, think of a classic up-and-down wave on a rope. Key features are crests (highest points) and troughs (lowest points).
- Longitudinal waves – the particles vibrate back and forth in the same direction as the wave travels. The classic example is sound waves. Instead of crests and troughs, they show compressions (where particles are close together) and rarefactions (where they are spread out).
Key terms to learn
- Wavelength (λ): distance between two corresponding points (e.g., crest to crest).
- Frequency (f): how many waves pass a point each second (measured in Hertz, Hz).
- Amplitude: maximum displacement from the rest position — linked to wave energy.
- Period (T): time for one wave to pass a point (T = 1 ÷ f).
- Wave speed (v): how quickly the energy travels through the medium.
2) The wave equation
The most important formula here is: v=f×λ
- v = wave speed (m/s)
- f = frequency (Hz)
- λ = wavelength (m)
You can find out more information from the BBC bitesize website here.
Exam tip: Check your units. Convert cm to m if needed, and always show working.
Example Problem:
A water wave has a frequency of 5 Hz and a wavelength of 2 metres.
What is the wave speed?
v=f×λ
v=5Hz×2m
v=10m/s
✅ Answer: The wave travels at 10 m/s.
How to use the wave equation in exams
- Write down the formula: v = f × λ.
- Rearrange if needed (e.g., f = v ÷ λ or λ = v ÷ f).
- Plug in the numbers (make sure units are correct).
- Show your working — the SQA gives marks for steps as well as the final answer.
3) The electromagnetic (EM) spectrum
The EM spectrum includes all transverse waves that travel at the speed of light in a vacuum. From longest wavelength to shortest:
Radio → Microwave → Infrared → Visible → Ultraviolet → X-ray → Gamma
You need to know:
- Uses (e.g., microwaves for cooking, X-rays in medicine).
- Dangers (e.g., UV causes skin damage, gamma is highly ionising).
- That all EM waves are transverse and travel at 3 × 10⁸ m/s in a vacuum.
4) Nuclear radiation
Nuclear physics is another key part of this unit. You should know:
- Alpha radiation: heavy, highly ionising, low penetration (stopped by paper).
- Beta radiation: medium ionising power, can be stopped by aluminium.
- Gamma radiation: very penetrating, weakly ionising, needs thick lead to stop.
Applications include medical tracers, radiotherapy, and industrial testing.
What Is Nuclear Radiation?
Atoms are made up of protons, neutrons, and electrons.
Some atoms have unstable nuclei. When this happens, they release nuclear radiation to become more stable. This process is called radioactive decay.
This radiation comes from the nucleus of the atom — not from chemical reactions — which makes it different from most everyday processes.
Types of Nuclear Radiation
There are three main types of radiation you need to know for the exam:
| Type of Radiation | Symbol | What it is | Penetration ability | Stopped by | Ionising ability |
|---|---|---|---|---|---|
| Alpha | α | 2 protons + 2 neutrons (a helium nucleus) | Low | Paper or skin | High |
| Beta | β | Fast-moving electron | Medium | Thin aluminium | Medium |
| Gamma | γ | Electromagnetic wave | High | Thick lead or concrete | Low |
5) Common exam questions
- Define a transverse wave → particles vibrate at right angles to direction of travel.
- Calculate wave speed given frequency and wavelength.
- Identify a wave from the EM spectrum used for medical imaging.
- State one similarity and one difference between alpha and gamma radiation.
Get more information from the BBC Bitesize website here.
FAQs: National 5 Physics – Waves & Radiation
Q: How do I remember the EM spectrum order?
A: A common mnemonic is “Raw Meat Is Very Unsanitary eXcept Grilled” (Radio → Microwave → Infrared → Visible → Ultraviolet → X-ray → Gamma).
Q: What’s the difference between alpha, beta and gamma?
A: Alpha = heavy, very ionising, least penetrating. Beta = medium properties. Gamma = highly penetrating, weakly ionising.
Q: Do all EM waves travel at the same speed?
A: Yes, in a vacuum they all travel at the speed of light (3 × 10⁸ m/s).
Q: How do I get better at wave calculation questions?
A: Practice using the wave equation with different units. Start with past-paper questions — repetition makes the formula second nature.
Conclusion – National 5 Physics exam
Mastering Waves and Radiation will give you a strong start in your National 5 Physics exam. By understanding the basics of wave types, practising the wave equation, learning the EM spectrum, and revising nuclear radiation, you’ll be ready to answer almost any question in this unit.
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