GCSE Physics Required Practical: Investigating Infra-red Radiation

Key Stage 4

Meaning

Investigate the relationship between the colour and reflectivity of a surface with the intensity of Infra-red emission.

Experiment 1: Leslie Cube

Variables

Independent Variable: The colour and reflectivity of each surface on the Leslie cube.

Dependent Variable: The temperature measured using an infra-red thermometer.

Control Variables: The volume of the water in the Leslie cube. The temperature of the water. The distance between the infra-red thermometer and the Leslie cube.

Method

A diagram showing several sides of a Leslie cube.

1. Pour hot water into the Leslie cube until it is full.
2. Use a ruler to measure 10cm from one surface of the Leslie cube.
3. Use an infra-red thermometer to measure the apparent temperature of the surface.
4. Record the apparent temperature and the colour/reflectivity of the surface.
5. Repeat for each of the 4 different surfaces of the Leslie cube.

Improving Accuracy

Complete the temperature readings very quickly to reduce the reduction in temperature of the water in the Leslie cube.

Place the Leslie cube on a on a heatproof mat to reduce the thermal energy lost to the table surface by conduction.

Improving Precision

Complete the repeat measurements as quickly as possible to reduce the range in the results.

Experiment 1: Painted Cans

Variables

Independent Variable: The colour and reflectivity of each surface on the cans.

Dependent Variable: The temperature change of the water after a given time.

Control Variables: The volume of the water in each can. The temperature of the water at the start of the experiment. The shape and size of the cans.

Method

A diagram showing the cans used in this experiment.

1. Set up the apparatus as shown in the diagram.
2. Measure 300ml of hot water (around 50°C) in a Measuring Cylinder.
3. Pour the hot water into one of the cans.
4. Wait until the temperature falls to 40°C and then start the stopwatch.
5. Record the temperature of the water every 30 seconds for 5 minutes.
6. Repeat steps 2-5 for each different colour/reflectivity of can.

Improving Accuracy

Place the cans on a heatproof mat to reduce the thermal energy lost to the table surface by conduction.

Place a lid over the cans to reduce the thermal energy lost to the air by evaporation.

Complete the experiments with different cans simultaneously so that a change in the temperature of the laboratory does not affect the results.

Place the measuring cylinder on a flat, level surface and read it from eye level to get an accurate reading of the volume of water.

A diagram including apparatus used improve the accuracy of an experiment to compare the effectiveness of different thermal insulators.

Improving Precision

Ensure the same amount of water is added to the cans (Control Variable) for each repeat measurement to reduce the range of results.