MYP Physics: Waves & Their Properties FAQ

The five properties MYP Physics expects you to know are amplitude, wavelength, frequency, period and wave speed. Amplitude measures maximum displacement from rest; wavelength is the distance between two identical points on the wave; frequency counts cycles per second; period is the time for one cycle; and speed links them through v = fλ.

A transverse wave vibrates at right angles to its direction of travel — light and water ripples are examples — while a longitudinal wave vibrates parallel to its direction of travel, like sound moving through air as compressions and rarefactions. MYP questions often ask you to sketch both and label crests, troughs, compressions and rarefactions correctly.

Use the wave equation v = fλ, where v is speed in metres per second, f is frequency in hertz and λ is wavelength in metres. Rearrange depending on what's missing: f = v/λ or λ = v/f. Always check your units match before calculating — that's the single most common mark loss I see in mock papers.

Amplitude is the maximum distance a point on the wave moves from its rest position, and it tells you about energy, not speed. Wavelength is the distance between two consecutive identical points on the wave, such as crest to crest. Mixing the two up on a labelled diagram is one of the most common errors I mark.

Start by naming the wave property being tested — frequency, wavelength, amplitude or speed — then apply v = fλ if a calculation's needed, or describe the behaviour (reflection, refraction, diffraction) using precise vocabulary. MYP markers reward correct units, labelled diagrams and a clear link between the observation and the underlying wave model, not just a final number.

MYP Physics wave questions typically use state, describe, explain, calculate and compare. 'State' wants a one-line fact — the wave equation, say; 'explain' needs cause-and-effect reasoning linking a property to a phenomenon; 'calculate' demands full working with units. Matching your answer's length and depth to the command term is what separates a level 7 from a level 5.

Describe reflection as a wave bouncing off a boundary at an equal angle of incidence and reflection, refraction as a wave changing speed and direction when it crosses into a different medium, and diffraction as a wave spreading out after passing through a gap or around an obstacle. Always name which property actually changes — direction, speed or spread.

The most common mistake is mixing up frequency and wavelength when reading a graph — students read the y-axis value for wavelength instead of measuring distance on the x-axis. Others forget to convert units before using v = fλ, or call diffraction 'bending' when it should be 'spreading out'. Watch your units and vocabulary closely.

Frequency (f) counts how many wave cycles pass a point per second, measured in hertz; period (T) is the time one cycle takes, measured in seconds. They're reciprocals — T = 1/f — so a wave with a frequency of 10 Hz has a period of 0.1 seconds. Mixing them up usually costs a mark on calculation questions.

It isn't conceptually difficult, but it demands precision — the topic rewards students who move fluently between diagrams, equations and everyday examples like sound and light. In years of teaching this unit, the students who struggle are the ones who memorise definitions without ever practising the wave equation on real numbers.

MYP waves lays the groundwork for the DP Physics 'Wave behaviour' theme, where you'll meet standing waves, the Doppler effect and superposition in far more mathematical depth. According to the IB, the current DP Physics guide (first exams 2025) groups wave phenomena under this dedicated theme, so a solid grip on v = fλ now saves real time at Diploma level.

MYP schools set their own unit assessments, but all must align with IB criteria — wave questions are usually marked under Criterion A (Knowing and Understanding) and Criterion C (Processing and Evaluating), each scored out of 8. Your child's report shows a criterion-level, not a raw percentage, which converts to the final 1-7 subject grade at year end.

Past unit tests, a labelled diagram of both the electromagnetic and sound spectrums, and a set of practice wave-equation calculations cover most of what's assessed. A revision guide with worked examples matched to each MYP criterion is more useful at this stage than a general textbook chapter your child has to decode alone.

A tutor's real value here is diagnosing exactly which criterion is weak — Knowing and Understanding versus Processing and Evaluating — rather than re-teaching the whole topic from scratch. One-to-one sessions turn a vague 'I don't get waves' into targeted practice on the wave equation, diagram labelling and command-term technique before the next assessed unit test.