St Peter's 13-18
1000 years ago, an Arab named Al-Haytham produced a remarkable seven volume treatise on the nature of light. Included in this work are accounts of scientific experiments and the use of the scientific method: techniques that predate the Western world by 600 years or so. To celebrate this anniversary, 2015 was named the International Year of Light in partnership with UNESCO. The St Peter’s Science department contributed their Christmas Lecture towards this celebration with a lecture called ‘Light Fantastic’.
In their section, the Chemistry department performed a Cinderella/Breaking Bad mash up. Mirrors were made in front of the audience’s eyes; slippers turned from glass to ordinary shoes and thermite reactions were used to break into safes. Mrs Greenhalgh showed some colourful flames, which demonstrate the intimate connection between light and electrons.
The Physics department continued the theme of obtaining light from electrons whilst demonstrating phenomena such as emission spectra, fluorescence and phosphorescence. We were fortunate enough to borrow a large phosphorescent screen from Cambridge University and Mr Parr used it together with a violet laser, to demonstrate his Jedi moves.
We have come a long way from Al-Haytham in understanding quite how strange light is. In particular we have to think of light as sometimes behaving like a wave and at other times as a particle. Light behaving as a wave explains colour effects such as iridescence whereas light behaving as a particle explains colour perception in the eye (as demonstrated by a full colour picture of a Mexican dancing Mr Winkley coming into view) and the photoelectric effect. We demonstrated the photoelectric effect using water pistols, air guns and a coconut shy.
The photoelectric effect is the first process of photosynthesis which provides a fundamental link between light and life. The Biology department examined this process further by demonstrating the fluorescence of chlorophyll – green plant extract turns blood red at the flick of a switch. Some animals have learnt to produce their own light and Mr Mallard told us a story of the predator prey relationships in the black depths of the oceans. Finally we were given some extraordinary examples of optical illusions by Mr Lawrence, who showed how to produce colour from nowhere that produced gasps of amazement from the audience.
The lecture ended with a tribute to the use of light as beacons, which was so essential to communication and our survival in the past. The pupils broke glow sticks up and down the tiered seating to make a link to the lecture in reverse as the beacon signal triggered a biological then physical and finally chemical process as the lit beacon was being observed.
As ever, huge thanks should go to the science technicians for the hours they put in and the level of skill they show in helping us to put together this lecture. Thanks to all the science colleagues who took part.