Electromagnetic Spectrum Simulation
This interactive simulation lets pupils explore the full electromagnetic spectrum by dragging a marker across a colour-coded spectrum bar spanning radio waves to gamma rays. The bar is rendered on a logarithmic scale — matching how physicists represent the spectrum — so the vast range from 1 MHz to 10²² Hz is navigable in a single sweep.
As the marker moves, a live metrics bar updates frequency (in appropriate units from MHz to EHz), wavelength (from km down to fm), photon energy in electron-volts (calculated from E = hf), and a rotating list of real-world uses for the current region. An animated waveform below the bar changes cycle density from region to region — long slow waves on the radio end, tightly packed oscillations toward gamma — giving pupils a visual sense of how wavelength shrinks as frequency rises. All values are calculated from c = 2.998 × 10⁸ m/s and E = hf, with region boundaries matching the AQA GCSE specification exactly.
Compare mode places a second marker on the spectrum simultaneously, revealing the frequency ratio between any two regions and reinforcing that all EM waves travel at the same speed regardless of frequency.
Class Activity — One Family, Eight Members
Year 10/11 · ~50 min · Pairs
Objective: Identify the seven regions of the EM spectrum, order them by frequency and wavelength, apply c = fλ, and explain why all regions share the same wave speed.
Hook (5 min) Open the simulation with no introduction. Ask pupils to drag the marker slowly from left to right and watch the frequency, wavelength, and waveform change. Ask: “What do you notice about wavelength as frequency goes up?” Take two responses. Ask: “What stays the same the whole way across?” Most will not spot the wave speed immediately — reveal it after a moment.
Direct Instruction (5 min) Point to the formula c = fλ on screen. Explain: all EM waves travel at c = 3 × 10⁸ m/s in a vacuum. This is not a coincidence — it is a property of electromagnetic radiation itself. Work through one example with pupils: at 100 MHz (FM radio), λ = 3 × 10⁸ ÷ 10⁸ = 3 m.
Guided Investigation (15 min) Pupils drag the marker to each of the seven regions and record from the metrics bar:
| Region | Frequency | Wavelength | One use |
|---|---|---|---|
| Radio | |||
| Microwave | |||
| Infrared | |||
| Visible | |||
| Ultraviolet | |||
| X-ray | |||
| Gamma |
For each row they also verify one calculation: check that f × λ ≈ 3 × 10⁸. The simulation displays both values simultaneously, so pupils can do the multiplication and confirm.
Compare Mode (8 min) Switch on Compare and ask pupils to place the two markers on radio and gamma. Read the frequency ratio. Ask:
- “Gamma frequency is how many times higher than radio?”
- “Despite this, do they travel at different speeds?”
- “So if both travel at c, what must be different between them?” (Wavelength and energy.)
Ask pupils to place the markers on infrared and visible. Ask: “Both of these are used by cameras. Why can we see visible light but not IR with our eyes?”
Exit Ticket (5 min)
- A microwave oven operates at 2.45 GHz. Calculate its wavelength.
- Place these in order of increasing wavelength: gamma, infrared, visible, radio.
- Why do all EM waves travel at the same speed in a vacuum?
Adaptation: Foundation pupils are given a partially completed table and use only the region labels and uses column, skipping calculation. Higher pupils are asked to calculate the energy in eV for two regions from E = hf, using h = 6.63 × 10⁻³⁴ J·s, and explain why gamma radiation is ionising and radio is not.