Understanding Physics: Waves: Edexcel IGCSE Science Single Award Explained

Waves carry energy from one place to another without moving matter, and understanding how they do it unlocks four specification topics at once

The waves section of the Pearson Edexcel IGCSE Science Single Award (4SS0) covers the properties that all waves share, the full electromagnetic spectrum, and the specific behaviours of light and sound. It is a section built on a handful of core ideas that are then applied to different contexts, which makes it efficient to revise: learn the principles once and you can answer questions across the entire section.

These edexcel igcse science single award revision notes work through each topic in the order the specification presents them. You will find key definitions, the wave equation with worked examples, a summary of the electromagnetic spectrum, and the optics concepts you need for the exam. Use these as your edexcel igcse science single award notes for structured revision, and finish with the self-check questions to test your recall.

Units

Quantity	Unit	Symbol
Angle	degree	degrees
Frequency	hertz	Hz
Wavelength / distance	metre	m
Wave speed	metre per second	m/s
Period	second	s

Properties of waves

Key definitions

The specification requires you to know the following terms:

Amplitude: the maximum displacement of a point on the wave from its rest (equilibrium) position. Larger amplitude means a louder sound or a brighter light.
Wavefront: an imaginary line joining points on a wave that are in phase (at the same point in their cycle). Wavefronts are perpendicular to the direction of wave travel.
Frequency: the number of complete waves passing a point per second, measured in hertz (Hz). A frequency of 50 Hz means 50 complete waves pass every second.
Wavelength: the distance between two consecutive points that are in phase (for example, from one crest to the next), measured in metres.
Period: the time taken for one complete wave to pass a point, measured in seconds. Period and frequency are related: period = 1 / frequency.

Waves transfer energy and information without transferring matter. When a wave passes through water, the water molecules oscillate up and down but do not travel with the wave. The energy moves forward; the material does not.

The wave equation

The relationship between wave speed, frequency and wavelength is:

v = f x lambda

where v is wave speed in m/s, f is frequency in Hz, and lambda is wavelength in metres.

Worked example: A sound wave has a frequency of 440 Hz and a wavelength of 0.77 m. What is its speed?

v = f x lambda = 440 x 0.77 = 338.8 m/s.

This is close to the speed of sound in air (approximately 340 m/s), which is a useful check.

This equation applies to all waves, including sound waves and electromagnetic waves. For electromagnetic waves in free space, v is always approximately 3.0 x 10⁸ m/s (the speed of light).

Reflection and refraction

All waves can be reflected and refracted. Reflection occurs when a wave bounces off a surface. Refraction occurs when a wave changes speed as it passes from one medium to another, causing it to change direction (unless it hits the boundary at right angles).

The electromagnetic spectrum

The electromagnetic spectrum is a continuous range of waves, all of which travel at the same speed in free space (the speed of light). The specification requires you to know the order of the spectrum from longest wavelength to shortest:

Type of radiation	Wavelength	Example uses	Potential hazards
Radio waves	Longest	Broadcasting, communication	Generally considered safe at normal exposure levels
Microwaves	Long	Cooking, satellite communication, mobile phones	Can heat body tissue (internal heating)
Infrared	Medium-long	Remote controls, thermal imaging, heating	Can cause skin burns
Visible light	Medium	Seeing, photography, optical fibres	Very bright light can damage eyes
Ultraviolet	Medium-short	Sterilisation, detecting fake banknotes, sunbeds	Sunburn, skin cancer, eye damage
X-rays	Short	Medical imaging (bones), airport security	Cell damage, cancer with excessive exposure
Gamma rays	Shortest	Sterilising medical equipment, cancer treatment	Cell damage, cancer with excessive exposure

Within the visible spectrum, the colours run from red (longest wavelength, lowest frequency) to violet (shortest wavelength, highest frequency). The mnemonic "Richard Of York Gave Battle In Vain" gives the order: red, orange, yellow, green, blue, indigo, violet.

Protective measures against harmful electromagnetic radiation include wearing sunscreen (UV), limiting exposure time (X-rays, gamma), using lead shielding (X-rays), and wearing protective goggles (UV, intense visible light).

Light and sound

Reflection of light

The law of reflection states that the angle of incidence equals the angle of reflection. Both angles are measured from the normal (an imaginary line perpendicular to the reflecting surface at the point of incidence).

Common mistake: Measuring the angle from the surface rather than from the normal. Always draw the normal first (a dotted line at 90 degrees to the surface), then measure both the incident angle and the reflected angle from that normal.

Refraction of light

When light passes from air into glass (or another denser medium), it slows down and bends towards the normal. When it passes from glass back into air, it speeds up and bends away from the normal. The specification asks you to investigate refraction using rectangular blocks, semi-circular blocks and triangular prisms.

A triangular prism separates white light into its component colours (dispersion) because different wavelengths of light are refracted by different amounts. Violet light bends the most; red light bends the least.

Total internal reflection and the critical angle

When light travels from a denser medium (such as glass) to a less dense medium (such as air), there is a special angle called the critical angle. If the angle of incidence is greater than the critical angle, the light does not pass through the boundary at all. Instead, it is totally internally reflected back into the denser medium.

Total internal reflection has two important applications specified in the course:

Optical fibres: Light enters one end of a thin glass fibre and undergoes repeated total internal reflection along its length, emerging at the other end. This allows information (such as internet data or telephone signals) to be transmitted as pulses of light over long distances with minimal loss.
Prisms: In periscopes and binoculars, 45-degree prisms use total internal reflection to redirect light beams through 90 or 180 degrees, replacing mirrors with a more durable and reliable component.

Sound waves

The specification states that sound waves can be reflected and refracted. Sound reflects off hard surfaces (producing echoes) and refracts when it passes between regions of different temperature or density (which is why sound can seem to carry further over water on a calm evening).

Self-check questions

Define amplitude, frequency and wavelength.
A wave has a frequency of 200 Hz and a wavelength of 1.5 m. Calculate its speed.
List the electromagnetic spectrum in order of increasing frequency.
Give one use and one potential hazard for each of: microwaves, ultraviolet radiation, and X-rays.
State the law of reflection.
Explain what happens when light passes from air into glass, in terms of speed and direction.
Define the critical angle and explain what happens when the angle of incidence exceeds it.
Describe how total internal reflection is used in optical fibres to transmit information.

How waves fits into the single award

The physics: waves edexcel igcse section is a mix of recall (the electromagnetic spectrum order, uses and hazards), calculation (the wave equation), and conceptual understanding (reflection, refraction, total internal reflection). The wave equation v = f x lambda is straightforward but must be applied correctly, with consistent units. The electromagnetic spectrum table is pure recall and rewards flashcard revision.

For your igcse 4ss0 physics: waves preparation, make sure you can list the electromagnetic spectrum in order, state one use and one hazard for each type, calculate wave speed from frequency and wavelength, and explain total internal reflection with reference to the critical angle. These are the areas that carry the most marks in the edexcel igcse exam.

Self-check questions

State two differences between the structure of a plant cell and an animal cell.
Describe the process of osmosis and explain why it is important in living organisms.
Explain the difference between an exothermic and an endothermic reaction, giving one example of each.
A car accelerates from rest to 20 m/s in 5 seconds. Calculate its acceleration and the resultant force if the car has a mass of 1200 kg.
Describe the structure of an atom, naming each subatomic particle and stating its relative charge and mass.

Self-check questions

State two differences between a chemical change and a physical change, giving one example of each.
Explain why a thermometer placed in a beaker of melting ice reads 0 degrees for several minutes even though heat is being supplied.
A student measures the voltage across a resistor as 6 V and the current through it as 0.5 A. Calculate the resistance and state the unit.
Describe how the structure of the small intestine is adapted for the efficient absorption of digested food molecules.

These edexcel igcse science single award notes give you the content; now put it to the test with edexcel igcse science single award practice questions from past papers. The edexcel igcse science single award explained approach works best when paired with active recall: close this page, sketch the electromagnetic spectrum from memory, and see how much you can reproduce. The Green Bridge CBT platform provides waves questions sorted by topic, allowing you to target your revision and measure your readiness before the exam.