Build a spectroscope to investigate light (and see rainbows!)

Child using a DIY spectroscope

 

Using just a few simple materials you can build a piece of scientific equipment that will allow you to investigate light sources and observe how they are different.

 

Making the spectroscope

You will need

  • A kitchen roll tube (or two toilet roll tubes)
  • A sharp pencil
  • Sticky tack or play dough
  • Scissors
  • A sheet of paper
  • A pencil
  • Sticky tape
  • An old CD

 

Sticking two toilet roll tubes together

 

1. If you’re using two toilet roll tubes stick them together with sticky tape. If you’ve got a kitchen roll tube, jump straight to step 3!

 

Ensuring no light enters the tube in the middle

 

2. You want to ensure that light only enters your spectroscope from the top, so we advise sticking a strip of paper around the join you made in step 1.

 

Making a small hole with a sharp pencil

 

3. Push the sharp pencil into the cardboard tube about 10cm from the bottom to make a small hole. It’s safest to push the pencil through the cardboard and into a lump of sticky tack.

 

Cutting a curved slit into the tube

 

4. Insert your scissors into the hole and, having flattened the tube slightly, make two slits angled towards the bottom of the tube.

 

Small rectangular peep hole cut into the tube

 

5. Use the sharp pencil and sticky tack technique to make another hole directly opposite the one you made in step 3. Insert your scissors and cut a small rectangle. This will be your peep hole.

 

Drawing around the end of the tube

 

6. Draw around one end of tube on the piece of paper.

 

Cutting a circle larger than the end of the tube

 

7. Draw a wider circle around the one you drew in step 6 and then cut it out.

 

Drawing the rectangle that will become a slit through which light enters the spectroscope

 

8. Draw a thin rectangle into the middle of the circle.

 

Cutting out the rectangle to make the slit for light to enter the spectroscope

 

9. Using the sharp pencil and sticky tack technique, make a small hole in the middle of the rectangle, insert your scissors and cut it out.

 

Preparing the paper cover to go onto the top of the spectroscope

 

10. Make small snips around the edge of the paper circle. These will make it easier to fold the edges of the circle down around the top of the spectroscope and stick them down.

11. Secure the paper circle to the top of your spectroscope using sticky tape.

12. Finally, slide your CD into the slits you made in step 4 with the silver shiny side uppermost.

 

Investigating light with your spectroscope

Start by taking your spectroscope outside. Do not point the top of your spectroscope directly at the sun. Instead point it towards a cloud and then put your eye to the peep hole to see what’s happening inside. What do you see?

Hint: you should see a rainbow inside the spectroscope! It may take you some time and adjustment to work out how best to hold it/where to look but persevere and you will be amazed.

But of course, sunlight isn’t the only type of light. How about carefully pointing the top of your spectroscope at other light sources and seeing what changes you notice?

Perhaps you can find and test these light sources?

  • Incandescent light
  • Fluorescent light
  • Neon light
  • Candle light
  • Star light

What do you observe? 

What is a spectroscope?

You’ve build a piece of scientific equipment that splits the light from a specific source so that you can easily see the different colours that make it up.

How does the spectroscope work?

The light we see is made up of lots of different colours of light, each with a different wavelength. The shiny surface of the CD is covered in a spiral of evenly spaced tracks. When the light travels down the spectroscope and hits the tracks it bends (defracts). Each colour of light has a different wavelength and so bends at a different angle. This means that the light is split, allowing you to see all the colours through the peep hole.

 

If you’d like to learn more about light, colours and rainbows, why not check out this video?