Unit Overview
Waves
CIE IGCSE Physics· 5 min read 📊 12-15% of total assessment, split across MCQ, structured and extended response questions
1. Unit at a Glance
The unit follows a logical learning arc: you will first master universal wave characteristics and behaviors, then apply these fundamentals to optical phenomena (light reflection, refraction, lenses), before moving to the electromagnetic spectrum and sound waves. Each subtopic builds directly on content from the prior one, so work through them in order to avoid gaps in understanding.
All content is tailored to common exam question scenarios, with clear links between abstract theory and real-world applications that are frequently tested in the 0625 assessment.
Work through the subtopics in the order listed below to build mastery incrementally:
General Properties of Waves
Defines core wave parameters, the wave equation, and universal wave behaviors including reflection, refraction and diffraction.
★★⏱ 8 min
Reflection and Refraction of Light
Explores the law of reflection, plane mirror ray diagrams, Snell’s law, and total internal reflection applications.
★★★⏱ 10 min
Thin Lenses
Covers converging/diverging lens ray diagrams, image characteristics, magnification calculations and practical lens uses.
★★★★⏱ 9 min
Dispersion and the Electromagnetic Spectrum
Explains white light dispersion, properties of each EM spectrum segment, and their real-world uses and safety hazards.
★★⏱ 7 min
Sound
Describes sound wave production, propagation, speed measurement, echoes, ultrasound applications and the human auditory range.
★★⏱ 7 min
2. Common Pitfalls
Wrong move:
Confusing wave speed, frequency and wavelength when a wave enters a new medium
Why:
Frequency of a wave does not change when crossing media, only speed and wavelength adjust
Correct move:
Use : if speed decreases in a denser medium, wavelength decreases proportionally while frequency stays constant
Wrong move:
Drawing converging lens ray diagrams with incorrect ray paths for objects inside the focal length
Why:
This leads to misidentifying if an image is real/virtual, upright/inverted or magnified/reduced
Correct move:
Always draw the three standard rays: parallel to axis through focus, through lens center unchanged, through near focus parallel to axis
Wrong move:
Mixing up uses of ultraviolet and infrared radiation in the EM spectrum
Why:
Both have common daily/industrial applications that are high-frequency exam questions
Correct move:
Link properties to uses: UV causes fluorescence, IR is used for thermal imaging and heating
3. Quick Reference Cheatsheet
Name | Formula/Key Rule | Subtopic |
|---|---|---|
Wave Equation | (speed = frequency × wavelength) | General Properties of Waves |
Law of Reflection | Angle of incidence = Angle of reflection, measured to the normal | Reflection and Refraction of Light |
Snell’s Law | (refractive index = sin(incidence angle)/sin(refraction angle)) | Reflection and Refraction of Light |
Describing an Image (Lenses) | Use enlarged / same size / diminished, upright / inverted and real / virtual (no magnification formula at IGCSE) | Thin Lenses |
EM Spectrum Order (lowest to highest frequency) | Radio, Microwave, Infrared, Visible, Ultraviolet, X-Ray, Gamma Ray | Dispersion and the Electromagnetic Spectrum |
Speed of Sound in Air | ~330 m/s at standard room temperature | Sound |
What's Next
Begin your study of this unit with the first subtopic: General Properties of Waves, which establishes the foundational vocabulary and equations you will use for all subsequent wave-related content. Once you have completed all subtopics in Unit 3, move on to Unit 4: Electricity and Magnetism, another high-weight area of the 0625 syllabus covering circuits, magnetic fields and electromagnetism.