Quick answer: The electromagnetic spectrum is the family of transverse waves that all travel at 3.0 × 10⁸ m/s in a vacuum, from radio waves through visible light to gamma rays. This grade 8 science lab on electromagnetic spectrum gives the aim, the equipment, the safety points, a step-by-step method, sample results and 8 analysis questions; the answers are on a separate page and the lab sheet is a free printable PDF.
Which parts of the electromagnetic spectrum pass through everyday materials? In this lab you test visible light, infrared from a remote control and radio waves with the same set of samples, and then compare what blocks each one.
Level: Grade 8 science (Year 9 · Class 8) · Curriculum: MS-PS4-3
Aim
To find which common materials block visible light, infrared from a remote control and radio waves, and to compare how different parts of the spectrum behave.
Equipment
- LED torch and a holder for samples
- Phone with a light-meter app (lux)
- TV remote control and a phone camera that shows infrared as a purple glow
- Small portable radio tuned to a station
- Samples: clear plastic sheet, white paper, cardboard, aluminium foil
Safety
Never put foil or any metal in a microwave oven. Do not look straight into the torch beam at close range. Use only a battery radio and take care with the sharp edge of the foil.
Method
- Point the torch at the light meter from 30 cm and record the lux reading with no material in the beam.
- Place each sample in the holder between the torch and the meter. Record the reading each time.
- Point the remote control at the TV through each sample and note whether the TV responds. Check with the phone camera that the remote’s light is visible.
- Tune the radio so that a station is clear. Wrap the radio fully in each sample in turn and record whether the signal stays clear, crackles or goes silent.
Results
Sample measurements from a school lab:
| Material | Light meter (lux) | Light passed (%) | TV remote works? | Radio signal |
|---|---|---|---|---|
| None | 820 | 100 | yes | clear |
| Clear plastic sheet | 760 | 93 | yes | clear |
| White paper | 310 | 38 | yes | clear |
| Cardboard | 0 | 0 | no | clear |
| Aluminium foil | 0 | 0 | no | silent |
Analysis questions
Question 1 Light through plastic
Check the percentage of light passed by the clear plastic sheet using 760 lux and 820 lux.Question 2 Light through paper
Calculate the percentage of light passed by the white paper.Question 3 Ranking the materials
Rank the five rows from most to least transparent to visible light.Question 4 Cardboard and radio
Cardboard blocks visible light but not radio waves. Explain what this shows about different parts of the spectrum.Question 5 Foil and radio
Explain why the radio went silent when it was wrapped in foil, and give one everyday example of the same effect.Question 6 Paper and the remote
The remote still worked through paper although only 38 % of the visible light passed. Suggest an explanation.Question 7 Uncertainty
The light meter readings fluctuate by ±10 lux. Calculate the percentage uncertainty in the paper reading and suggest how to reduce it.Question 8 Predicting tracing paper
Predict the lux reading, the remote result and the radio result for a sheet of tracing paper, and justify your answer.
