Primary colours (IMPROVED)
This is a totally new way of demonstrating combining primary colours of light that does not require filters or lamps. Depending on age and ability the activity takes 30-50minutes. Overview: The presentation deals with the visible spectrum, primary colours and the eye. If the presentation is shown through a data projector, the projector itself acts as a high intensity light source. This means that: 1) You can split up a beam of white light using a prism (slide 4)- the spectrum looks awesome if projected onto a distant wall. 2) You can also use small mirrors to reflect and combine the primary colours (slide 16)- it takes some practice but it works supprisingly well. It is best in a darkened room although this is not entirely necessary. Summary of the remaining slides: Slide 18: The question could asked- 'If white light can be split into the full spectrum- why do we only need to combine red, blue and green light to make white?' This may lead to a discussion of red, blue and green photo-sensitive cells in the eyes; the after image illusion demonstrates the effects of this. Slide 21-36: Students love these illusions. Leave the inverted images up for 30 seconds and ask students to stare at them. After the 30 seconds show a white screen and ask students to blink. They should see an after image with the correct colours. Slide 24 It is worth allowing students time to write how they would design the illusions in the list. This will test whether they understand the principle. Once they have decided what colours would go where- show the working illusions. *I have added the flags / objects in their correct colours to help students design the after image illusion. I have also added questions at the end for AFL and some questions for deeper discussion


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Created: Nov 9, 2009

Updated: Oct 24, 2013

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Primary colours modified

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