Pupils switch on to the marvel of light and colour

Scientist Ben Craven tours schools, teaching their intriguing properties and how the brain perceives them. Jackie Cosh reports

Why do we live in a world full of colour? Which creature has the best colour vision - dog, pigeon or human? The questions - along with intriguing-looking boxes on the table - are keeping the fifth-year Higher physics class mesmerised.

Dr Ben Craven (pictured left) is a freelance scientist with a background in colour vision. His CV includes working on hands-on exhibitions for the Glasgow Science Centre, devising and building various original science demonstrations and exhibit prototypes, and creating and working on shows for the Edinburgh Science Festival. Today, as part of his work with The Colour Group, he is giving a talk on colour to pupils at Hyndland Secondary in Glasgow.

"Different-coloured lights don't look different, but our brains make things look different," explains Dr Craven. "In order to make compensations, our brain assumes light has different properties."

He gives the example of clothes which look as if they match when held up together in the shop, but which obviously don't when examined outside. Or car re-sprays which look perfect until taken out into natural light.

"We are good at allowing for change in light and adapting to light," says Dr Craven. "Two lights can be the same in physics terms, but stimulate the brain differently. We are all colour blind but to one less degree than the standard red-green."

When Carol Monaghan, joint faculty head of science, received an email from Science Connect, inviting schools to get in touch if they would like a visit, she jumped at the chance.

"It sounded interesting," says Mrs Monaghan. "Anything that doesn't involve taking the pupils out of school is fantastic as that can be time- consuming. And it is great to have someone who has such expertise."

The issue of colour blindness is central to the talk, as is the concept of the illusions the brain creates. To demonstrate, he presents the class with a specially-made box with two cubicles. Both are illuminated with what looks like identical light until half a red pepper is placed in each. In the top, the red colour of the pepper appears strong and bright; in the lower cubicle the pepper is dull and almost colourless.

In another experiment the class is shown a lit square which appears to be white, until a darker one is placed beside it, making it look light grey. When a third dark grey square is placed beside the other two, the first now looks very dark.

"All the time, the brain is doing colour calculations to compensate," says Dr Craven. "Normally, the brain is good but occasionally it gets it wrong."

As well as showing various experiments, he presents the pupils with some interesting facts. They learn that the colours of fireworks come from having different chemicals in them and that this is helpful for astronomers as it allows them to tell what a star is made out of from its colour.

They learn that as far as pigeons are concerned, we are colour-blind because they have four different colour cells, whereas humans have only three, and that many reptiles and fish have better colour vision than we do.

But he also poses questions - what colour do you see when you close your eyes? How can you turn black into white?

What started off as a physics talk is now incorporating the other sciences such as biology and, in many ways, psychology. Dr Craven does stress that it is as much about biology and psychology as physics and many of his experiments are designed to show how the brain perceives colour.

All this has given Mrs Monaghan some ideas for future lessons. "It made me think, `Could we reconstruct the experiments?' They are so simple, and as a department we will look at taking things on," she says.

Later in the morning, Dr Craven will be adapting the talk for other groups from first year to Advanced Higher. From what she has seen, Mrs Monaghan is certain that all ages will be interested.

"It fits into aspects of the curriculum," she says. "Colour is covered in Standard grade physics, but at Higher level we are giving them something to engage them, to give them an interest in science. And the first and second years are now covering work which years ago would have been covered later on in the school."

The class has sat quietly throughout and it is not until the very end that a pupil asks Dr Craven a question: "Does the lighting outside affect how we see things?"

"It is great when students ask questions I have never thought of," says Dr Craven. "Perhaps on Mars, everything would seem pink. We don't know yet. The brain has been designed through evolution."

"We expect lots of questions next week," says Mrs Monaghan. "And Dr Craven says we can email questions over to him. This group are quiet but what we will find is that they ponder things."



The Colour Group is an interdisciplinary society of scientists concerned with the measurement, reproduction and perception of colour.

It organises lectures and meetings on the subject of colour. Its objective is to encourage the study of colour and to promote the education of the public on colour.

As part of his work with The Colour Group, Dr Craven gives demonstration- based talks on the science of colour to school groups from ages nine to 18. Talks are linked to the curriculum but are also designed to encourage an interest and curiosity in the subject, rather than being totally fact- based.

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