MYP Science: Light & Sound — Concepts, Command Terms and How to Answer Exam Questions

MYP 1-3 Science covers wave basics: how light reflects, refracts and travels in straight lines, and how sound needs a medium and moves through vibrations. You'll study frequency, wavelength, amplitude and wave speed, plus applications like echoes, the electromagnetic spectrum, and how the ear and eye actually detect these waves.

Reflection is light bouncing off a surface at the same angle it hit it — the angle of incidence equals the angle of reflection. Refraction is light bending as it passes from one medium into another, like air into water, because its speed changes. Mirrors reflect; lenses and prisms refract.

Sound is a mechanical wave — it needs particles (a medium) to travel, so it moves through air, water or solids but not through a vacuum. Light is an electromagnetic wave that doesn't need a medium, which is why sunlight reaches Earth through empty space but you'd hear nothing at all in orbit.

Sound is a series of vibrations passed from particle to particle, so with no particles in a vacuum, there's nothing to vibrate and no wave forms. Light is electromagnetic — a self-propagating oscillation of electric and magnetic fields that needs no medium, which is exactly how sunlight crosses roughly 150 million km of empty space to reach us.

Start by identifying the command term — 'describe' wants what happens, 'explain' wants why. Then answer using the correct scientific vocabulary from the unit (reflection, refraction, frequency, wavelength, amplitude, medium), not everyday language, and always link the observation to the mechanism behind it rather than just restating what you saw.

In MYP 1-3, the command terms you'll see most often are describe, explain, state, outline, compare, distinguish and calculate. 'Describe' wants observable detail — what you'd see or hear — while 'explain' wants the reasoning behind it, using terms like reflection, refraction or vibration correctly.

Use the wave equation: speed = frequency × wavelength (v = fλ), where speed is in metres per second, frequency in hertz and wavelength in metres. Rearrange it to find any missing value — frequency = speed ÷ wavelength, or wavelength = speed ÷ frequency — and check your units line up before you calculate.

The biggest one I see in Years 1-3 is mixing up frequency and amplitude — frequency changes pitch (or colour, for light), amplitude changes loudness (or brightness), not the reverse. The second is describing refraction as 'light bending because of the surface' instead of because its speed changes crossing into a different medium.

Light and sound units get assessed against the same four MYP Sciences criteria used across all units: Criterion A (Knowing and understanding), Criterion B (Inquiring and designing), Criterion C (Processing and evaluating) and Criterion D (Reflecting on the impacts of science). A typical unit usually combines A and B through content tests and a practical investigation.

In MYP 1-3, expect shorter tests focused on Criterion A recall and simple Criterion B investigations, like measuring angles of reflection or testing pitch with elastic bands. By MYP 4-5, the same topics return with heavier mathematical demand — wave equations, EM spectrum calculations — and fuller Criterion C data analysis, feeding straight into DP Physics.

Common ones include measuring the angle of reflection with a ray box and mirror, testing how pitch changes with the length or tension of a vibrating string, and checking how loudness changes with distance from a speaker. Each links directly to Criterion B (planning) and Criterion C (analysing your results honestly, including anomalies).

According to the IB, the current Physics guide (first exams 2025) builds its Waves topic directly on foundations first introduced in MYP 1-3 — frequency, wavelength, refraction. A student comfortable rearranging v = fλ in Year 2 has a real head start when the same equation reappears with harder numbers at Diploma level.

Not conceptually — most students grasp reflection and vibration quickly because they're visible, everyday phenomena. Where they lose marks is vocabulary precision and the maths: rearranging v = fλ, or explaining refraction as a speed change rather than a vague description. It's a manageable topic with focused practice, not one that needs alarm.

Look for materials organised by the actual MYP unit, not generic 'physics for kids' content — topical worksheets with reflection and refraction diagrams to label, short vocabulary recall questions, and mock-style questions phrased with genuine command terms like 'describe' and 'explain'. That's more useful to a Year 7 student than a general science workbook covering everything at once.