Colours. We see them every day. Like at this moment: Your classroom, your laptop, tablet or PC and also the screen on which you see this website appear to you in colour. But why is that? How do the different colors come about?
As an introduction, watch this video and take notes on the following questions:
- What are the characteristics of a light wave? Describe them
- What is the light spectrum?
- What is the differnce between red light and purple light?
- What has to happen to the sunlight in order for you to see an object as white or black?
Let us now take a closer look at light and colour with some experiments.
For the first one, you will need:
- 3 luminaires with power sources
- 3 slide holders
- 3 colour filters (red, green, blue)
- One white shield
Task 1: Take the lamps, the slide holders, the colour filters and the white shield. First connect the first lamp and place the red colour filter in the slide holder in front of it. A red rectangle should appear on the screen. Now take the second lamp, place the second slide holder in front of it and put the green colour filter in. A green rectangle should now appear on the screen next to the red one. We now recreate the arrangement of the coloured boxes on the screen as shown here on the right. So, you add the third lamp with the blue colour filter in the third slide holder and overlap the light boxes as shown on the right. What colours are created when the three primary colours overlap?
Task 2: Document your experiment and your results in the form of an experimental protocol.
Task 3: Think about it: Do your results of mixing the light colours green, blue and red match how you are used to mixing the colours? What is different? Consider this thought in your notes on the items „Results“ and „Interpretation“ in the experimental protocol.
We will now get to the bottom of this difference between the colour mixtures with a second experiment. This time you need:
- An overhead projector
- One colour filter each in cyan (light blue), yellow and magenta (purple)
Task 4: Now arrange the three rectangular colour filters over the surface of the OHP in the same way as the coloured rectangles on the screen in the last experiment (see illustration above) and switch on the OHP. What do you see on the wall? How do the colours mix here? Also document this experiment in an experimental protocol.
More on that on the next page
Lights on! 