Chemical photography is a specific technique that allows scientists to look within objects to discover the chemicals inside. This has uses in all sorts of areas: forensic science, creating new medicines, and even discovering fake artworks!
Infrared in a shoebox
See students' sheet for full instructions on how to set this up. This procedure has been modified from an experiment on http://coolcosmos.ipac.caltech.edu/ (NASA/JPL-Caltech), which also has other useful information on infrared spectroscopy.
This experiment can be done in groups of two or four, depending on the class size. You may want to save time by pre-cutting the boxes (this has been left in the student procedure as you may like to ask them to do this) and painting and taping the thermometers before the l
The temperatures of the colours should increase from the blue to red part of the spectrum. The highest temperature should be just beyond the red part of the visible spectrum. This is the infrared region. You can discuss these other forms of light as an extension to the experiment.
You can also get the students to measure the temperature of other areas of the spectrum, e.g. the area just beyond the blue. You can also try the experiment at different times of the day.
For more information about Chemical Photography visit www.imperial.ac.uk/vsci.
Glass prism - don't use plastic prisms as they don't work
Alcohol thermometers - three per group
Permanent black marker or black paint
Scissors or a
Blank sheet of white paper
Safety: Wear safety glasses. A risk assessment must be done for this activity.
(relates to the What's next section of the students' sheet)
The bulbs of the thermometers are blackened to absorb heat more efficiently and the temperatures of the colours should increase from the blue to red part of the spectrum.
The highest temperature should be just beyond the red portion of the visible light spectrum which is the infrared section.
Ultraviolet light, X Rays and radio waves are all invisible parts of the spectrum. You can extend the activity by measuring the temperature of ultraviolet light.
|Chemical and Material Behaviour||6d: The properties of a material determine its uses|
|Energy, electricity and radiations||7c: Radiations, including ionising radiations, can transfer energy|
|7d: Radiations in the form of waves can be used for communication|
Applicable examination units:
P1b: The uses and hazards of the electromagnetic spectrum
WJEC: GCSE Science
P2: Electromagnetic radiation and the Universe
The electromagnetic spectrum
Scottish Curriculum: Standard Grade Physics
Unit 7: Space Physics
Section 1: Signals from space
Northern Ireland Curriculum: GCSE Single Award Science
5: Electricity, waves and communication
Northern Ireland Curriculum: GCSE Double Award Science
3.6: Waves, light and sound, electricity, and magnetism, Earth in space
Northern Ireland Curriculum: GCSE Physics
3.3 Waves, sound and light
Science for you to try
Infrared in a shoe box
The research team from Imperial College London use infrared light to produce 'chemical photographs' of objects. But infrared is outside of the visible spectrum, so how was it discovered?
Try this experiment and follow in the footsteps of Sir William Herschel, a British astronomer and Fellow of the Royal Society, to find out.
You will need:
- Glass prism
- 3 Alcohol thermometers
- Permanent black marker or black paint
- Scissors or a prism stand
- Cardboard box
- Blank sheet of white paper
Safety: Wear safety glasses.
The experiment should be done outdoors on a sunny day. The setup is shown below.
1. Place the sheet of white paper flat in the bottom of the cardboard box.
2. Take three thermometers and blacken the bulbs by painting them with black paint, or colouring them with a black marker pen.
3. Attach the glass prism near the edge of the box facing the sun. If you don't have a prism stand you can place the prism in a rectangular cut in the top edge of the box. This should hold the prism snugly, but you should still be able to rotate the prism.
4. Rotate the prism until you get the widest possible spectrum on the white sheet of paper. You may have to tilt the box.
5. After securing the prism in place, put the thermometers in the shade and record the air temperature. Then place the thermometers in the box so that one of the bulbs is in the blue region, another is in the yellow region, and the third is just beyond the red region.
5. Record the temperatures in each of the three regions of the spectrum: blue, yellow, and just beyond the red every minute for a total of five minutes.
6. Calculate the difference between the final temperatures measured in the spectrum and the shade for all three thermometers.
Herschel's experiment was important not only because it led to the discovery of infrared light, but also because it was the first time that it was shown that there were forms of light that we cannot see with the naked eye.
- Why do you think you had to blacken the thermometer bulbs?
- Which thermometer recorded the highest increase in temperature? Why do you think this is?
- There are many other types of electromagnetic radiation that we cannot see, can you name some of these? Hint, one of them lies beyond the other end of the visible spectrum.