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

esson.

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.

Materials required

Glass prism - don't use plastic prisms as they don't work as well
Alcohol thermometers - three per group
Permanent black marker or black paint
Scissors or a

prism stand
Cardboard box
Blank sheet of white paper

Safety: Wear safety glasses. A risk assessment must be done for this activity.

Discussion

(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.

 

Curriculum links

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:

Exam Board
Unit

AQA:GCSE Science

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

fingerprint

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.

 

 

Procedure

Download a pdf of the instructions here.

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.

Set-up for infra-red experiment

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.

Spectrum 2

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.

What's next?

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.

  1. Why do you think you had to blacken the thermometer bulbs?
  2. Which thermometer recorded the highest increase in temperature? Why do you think this is?
  3. 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.