The magic of light
The lead up to Christmas is a good time to think about light. Dark days are cheered up with sparkling
fairy lights and candles and we can be dazzled by a brilliant sun on a cold and crisp winter’s day.
We started our unit by considering different light sources and grouping them into natural and
artificial light sources. Straight forward you would think – not in this class! We ended up having a
debate about whether fireworks were man made light sources or artificial. The discussion generated
lots of interesting thoughts and questions. Sorting the moon was also interesting. About a third of
the class thought it was a light source. To help us to understand that it reflected sunlight we dug out
torches, mirrors and tennis balls covered in silver foil.
But what is light? Our observations using our spectroscopes showed us that white light can be split
into the colours of the rainbow. Looking carefully at phone and I pad screens we could identify tiny
little dots of colour – pixels. Well, the children concluded, they must be mixed together, like you do
in art.
Splitting light using our spectroscopes
This brought us to our first experiments using colour wheels. The children picked two basic colours
to colour their wheels in with. Before spinning their wheels they hypothesised about what colours
they thought they would see based on their understanding of primary and secondary colours in art.
By the end of the session children recognised that light produces basic and complex colours – and
interestingly although very similar to those used in art classes, it was not exactly the same. They also
learnt a lot about constructing an effective colour wheel. This would help them when we came to
our next big question:
In mixed age groups the children considered the question carefully. Some were convinced that they
would get a muddy, greeny, brown colour, similar to colour you produce when you mix paint
together but some children wondered if you would see white because if you split white light you get
the colours of the rainbow, so if you mix them up surely you will get white.
A template was produced and the children set about their task. They worked in groups of three –
helping each other out with the spinning and observations and repeating each spin several times.
Our results:
In a word, curious. Why did some groups see browns, purples, greens and why did some groups see
white? One group saw white in the middle but light brown on the outside. It got us thinking …….
We decided we would find out what we should have seen. Ben was the first person to turn with an
answer having done his research at home. It was true – the colours on our colour wheel should have
‘disappeared’ and turns white as the wheel was spun around.
As ever our experiments generated as many questions as they answered! Did it make a difference
about how quickly the wheel span? Did it matter what order the colours were in on the wheel? Did it
matter what shades the colours were? Did some shades of pens/crayons/felt tips work better than
others?
If we ever got an opportunity to redo this experiment we decided we would consider these
questions carefully, especially when setting up the task and recording our observations.
KS2 Brennand’s Endowed Primary School, Slaidburn
December 2016