Have you ever wondered how helium, that party balloon gas, got its name?

When elements burn, the light that they produce can be analysed using a spectroscope. Each element produces a unique pattern of coloured lines (spectrum) like the elements above, when the light is split into its different parts.

In 1868 a solar eclipse meant that it was safe to observe the sun and perform an analysis of the spectra of its outer parts.  Astronomers found a new pattern of spectral lines which had never been observed on Earth.  A new element had been discovered and was named helium, after the Greek word helios, meaning Sun.

You can build your own spectroscope using a few simple materials and use it to look at the differences in the light given off by different sources.

  1. Take your kitchen roll tube and insert the black card so that it lines the inside. Then carefully cut off any excess and tape it in place.
  2. Take the remaining piece of black card and place the kitchen roll tube upright on top of it. Draw and cut out a circle that is 1cm wider than the end of the tube.
  3. Cut out a rectangle in the middle of your circle then stick the circle to one end of the kitchen roll tube.
  4. Next,taking the remaining card, cut two smaller rectangles and tape them either side of the central rectangle so that only a narrow slit is left open. It’s very important that the final slit is straight and level at either side.
  5. Take your CD and stick it onto the other end of the kitchen roll tube so that you can look through the transparent part and into the tube.Check that everything is secure and there are no gaps in your spectroscope, then hold it up to a fluorescent light while looking through the CD end of the tube. Do not put your eye directly to the CD, keep a distance of at least 15 cm. You should see a colourful, rainbow-like spectrum on the transparent surface of the disc. This works especially well if you cover one of your eyes.

How it works: The spectroscope is splitting the light into the colours of the rainbow. The CD screen bends the light as it passes through, filtering the wavelengths of the white light so that you can see all the colours of the spectrum. Try looking at different light sources like the TV, computer screen, or LED displays and see whether the spectrum of colours you can see is any different. YOU MUST NEVER LOOK DIRECTLY AT THE SUN AS IT CAN DAMAGE YOUR EYESIGHT.

Why not try taking some photos of different light sources using your spectroscope and sending them to us here at The Left-Handed Lemon blog?  You could win a prize if we like your work!

If you want to have a go at tomorrow’s activity, you will need a pestle and mortar or something similar as well as samples of natural materials you can crush, eg berries, clay, charcoal, leaves etc.

Until next time, Keep calm and apply some Science.

This activity has been taken from the downloadable pack at https://www.britishscienceweek.org