Quick answer: Light is a form of energy that travels in straight lines called rays. This grade 6 science lab on how light travels gives the aim, the equipment, the safety points, a step-by-step method, sample results and 7 analysis questions; the answers are on a separate page and the lab sheet is a free printable PDF.
Which materials let the most light through, and does light really travel in straight lines? In this lab you use a torch and a light meter to measure transmission through five samples, then test the straight-line idea with three punched cards.
Level: Grade 6 science (Year 7 · Class 6) · Curriculum: MS-PS4-2
Aim
To measure how much light different materials let through, to classify them as transparent, translucent or opaque, and to test that light travels in straight lines.
Equipment
- Torch with a fresh battery
- Light meter (or a light sensor with a display)
- Metre ruler and sticky tack
- Samples: clear plastic, tracing paper, bubble wrap, cardboard, aluminium foil
- Three index cards with a hole punched in each
Safety
Never shine a torch or any bright light into someone’s eyes. Handle the foil and punched cards carefully because their edges can be sharp.
Method
- Fix the torch, the sample holder and the light meter on the ruler, 10 cm apart, in a dim room.
- With no sample in the holder, switch on the torch and record the reading three times.
- Put in each sample in turn. Record three readings each time.
- Calculate the mean and the percentage of light passing through.
- Finally stand the three punched cards on the ruler in a line, 10 cm apart, and look through the holes towards the torch. Then move the middle card sideways.
Results
| Sample | Trial 1 (lux) | Trial 2 (lux) | Trial 3 (lux) | Mean (lux) |
|---|---|---|---|---|
| No sample | 120 | 121 | 119 | to calculate |
| Clear plastic | 112 | 110 | 114 | to calculate |
| Bubble wrap | 90 | 92 | 88 | to calculate |
| Tracing paper | 66 | 64 | 65 | to calculate |
| Cardboard | 0 | 0 | 0 | to calculate |
| Aluminium foil | 0 | 0 | 0 | to calculate |
Analysis questions
Question 1 Mean readings
Calculate the mean reading for no sample, clear plastic, bubble wrap and tracing paper.Question 2 Percentage transmitted
Calculate the percentage of light that passes through clear plastic, bubble wrap and tracing paper, to the nearest per cent.Question 3 Classify the samples
Classify all five samples as transparent, translucent or opaque, using your results and how clearly you could see through them.Question 4 Ranking
Rank the samples from the one that lets most light through to the one that lets least.Question 5 Fair test
State three variables that you kept the same and explain why.Question 6 Straight line test
Explain what you saw with the three cards and what this shows about light.Question 7 Improving accuracy
Suggest two ways to improve the accuracy of the readings.
