Leslie's Cube & Other Radiation Experiments
Physics: Cambridge International GCSE Supplement, topic 2.3.7
Radiation Experiments
Painted thermometer bulbs
- Setup: Take two thermometers. Paint one bulb black and leave the other shiny silver. Place them side by side in front of a radiant heat source (like a heat lamp).
- Observation: The black bulb thermometer rises in temperature more quickly than the shiny one.
- Explanation: A black surface is a good absorber (and also a good emitter) of infrared radiation.
- A shiny silver surface is a poor absorber (it tends to reflect radiation).
- Conclusion: Surface colour and texture affect how well radiation is absorbed and emitted.
Hot water in different coloured metal beakers
- Setup: Fill two identical metal beakers with the same amount of hot water. One beaker is painted black, the other is left shiny silver. Measure how quickly the water cools.
- Observation: The black beaker cools down faster than the shiny silver beaker.
- Explanation: A black surface is a good emitter of infrared radiation, so it loses heat more quickly.
- A shiny silver surface is a poor emitter, so it keeps the water hot for longer.
- Conclusion: Black surfaces are good absorbers and emitters of radiation, while shiny surfaces are poor absorbers and emitters.
Test yourself on Leslie's Cube & Other Radiation Experiments
Explain how Leslie's cube works.
Which of the following statements is true, in connection with Leslie's cube?
What do we call the box with 4 different colour sides that is used to measure the rate of radiation emission?