Years 7–10 · Week 2 of 12
Waves, Particles and Light
Learning goals
By the end, you can…
- Describe wavelength, frequency and amplitude in a simple wave model.
- Relate photon energy conceptually to light frequency.
- Compare wave-like patterns with localised photon detections.
- Explain why neither a water wave nor a tiny classical ball is a complete model of light.
What you already know
Connect to a familiar idea
You may have described light using rays and waves. Those models explain many observations, but experiments also record light in individual, localised energy-transfer events called photon detections.
- Waves can transfer energy.
- Graphs can show repeating patterns.
- Light can be detected with instruments.
Opening story
Start with something familiar
A dim light shines on a sensitive detector. Instead of a smooth trickle, the detector registers separate events. After many events, their overall distribution can still form a pattern predicted using a wave-like quantum state.
Plain-English explanation
Build the idea carefully
What a wave model describes
Wavelength is the distance between matching points of a repeating wave, frequency counts cycles per second, and amplitude describes the size of a wave disturbance in a chosen classical model. For light in vacuum, higher frequency corresponds to shorter wavelength; photon energy also increases with frequency.
Photons and complementary evidence
Interference and diffraction are wave-like features, whereas a light detector exchanges energy in localised photon events. The words 'wave' and 'particle' identify useful patterns in evidence. A photon is not fully described as either a water ripple or a tiny hard ball following a known classical path. The experimental question and apparatus determine which features can be observed and which model is useful.
Try the model
Adjust a wave and collect detections
Change wavelength and amplitude, then add photon-detection events and compare individual events with the accumulated distribution.
Ready. Adjust a control, then run the model.
What this model shows: The animation links model parameters to predicted patterns; it is not a video of a photon travelling as a drawn sine curve.
Text alternative for this interactive
Wave table and event sequence Compare three labelled wavelengths and read a numbered list of detector positions whose histogram builds over time.
Expected observation: Detections arrive as separate events, while many events can build a distribution with wave-like structure.
Guided activity
Two descriptions, one evidence table
- Record what changes when wavelength is shortened.
- Record what one detector event can and cannot reveal.
- Use at least fifty events to describe the accumulated pattern.
- Match each observation to wave, photon or combined quantum language.
Evidence to collect: A comparison table that links wave-like patterns and localised detections to observations without treating either classical picture as complete.
Glossary
Words to know
- wavelength
- The distance between corresponding points of successive cycles.
- frequency
- The number of cycles per second, measured in hertz.
- amplitude
- The size of a disturbance in a specified wave model.
- photon
- A quantum of electromagnetic energy and momentum.
- detection event
- A localised recorded interaction with a detector.
- interference
- A pattern produced when amplitudes combine.
Short recap
Keep these ideas
- Wavelength, frequency and amplitude describe features of wave models.
- Light transfers energy in localised photon-detection events.
- Quantum light shows features that neither a classical water wave nor a tiny hard ball fully describes.
Knowledge check
6 clear questions
Choose an answer for immediate feedback. You may retry, and your best submitted score is kept.
Go Further Optional extension for Years 9–10
For Years 9–10, use the proportional relationship between photon energy and frequency, E = hf, qualitatively. Doubling frequency doubles the energy per photon; no value of Planck's constant is required.
Try this
Rank red, green and violet photons by frequency, wavelength and energy, then explain why brightness and energy per photon are different ideas.
Adult support Teacher and parent notes
Discuss
- Keep amplitude language tied to a specified model; do not equate a drawn wave height directly with photon size.
- Ask students to identify observations before choosing particle or wave words.
Answer guidance
Accept 'wave-like' and 'particle-like' only when students name the supporting observation, such as interference or localised detection.
Offline activity
Use a slinky only to review wavelength and amplitude, then make a separate dot plot to emphasise that the analogy does not model photons.
Safety
Do not conduct laser demonstrations unless the school has an approved risk assessment, suitable equipment and trained supervision.
Sources and further reading
Checked references for this lesson
These sources support the lesson’s main scientific claims. Links open on the source organisation’s site.
- Wave-Particle Duality OpenStax, Rice University · open textbook · checked 2026-08-02
- Quantum information science National Institute of Standards and Technology · government explainer · checked 2026-08-02
Content review: Reviewed on 2026-08-02.