SQA National 5 Physics Area 5 Waves: a complete overview of wave parameters, the electromagnetic spectrum and refraction

Area 5 Waves is about how energy travels as waves, the family of electromagnetic waves, and how light bends. It has three key areas; each has its own answer page with worked examples, and this guide ties them together.

Wave parameters and behaviours

A wave carries energy without carrying matter. The key quantities are wavelength ($\lambda$), frequency ($f$), period ($T$), amplitude and speed ($v$), linked by $v = f\lambda$ and $f = \frac{1}{T}$. Waves are transverse (vibrations across the travel direction, like light) or longitudinal (vibrations along it, like sound). They can be reflected (echoes, mirrors) and diffracted (spread round edges and through gaps), with longer wavelengths diffracting more.

The electromagnetic spectrum

The electromagnetic spectrum is a family of transverse waves that all travel at the speed of light ($3.0 \times 10^8 \text{ m s}^{-1}$ in a vacuum). In order of increasing frequency the bands are radio, microwave, infrared, visible light, ultraviolet, X-ray and gamma. Each has its own uses and detectors (for example, infrared for remote controls and thermal imaging, X-rays for medical images), and the high-frequency bands carry more energy and can be dangerous. The relationship $v = f\lambda$ applies with $v = c$.

Refraction of light

Refraction is the bending of light at a boundary, caused by a change of speed. Going into a denser material light slows and bends towards the normal; going into a less dense material it speeds up and bends away. The angles are measured from the normal. A lens focuses light by refraction, and total internal reflection (when the angle inside a dense material exceeds the critical angle) keeps light bouncing along an optical fibre.

How Waves is examined

Waves questions combine calculations ($v = f\lambda$, $f = \frac{1}{T}$, $v = \frac{d}{t}$, and the speed of light for the spectrum) with recall and explanation (the order of the spectrum, uses and detectors, why light refracts, total internal reflection). For calculations, convert units carefully (MHz to Hz, and watch the powers of ten for the speed of light). For explanations, link refraction to a change of speed and measure angles from the normal.

For the official course specification

The SQA publishes the full National 5 Physics course specification, data sheet, relationships sheet and past papers at sqa.org.uk. Always revise from the current specification and SQA past papers.