A STEM Afternoon With Polarised Light and Microscope

Polar Bear Fur at 100x magnification between crossed polarisation filters

Thirty year 3 primary school students, arranged in a horseshoe jostled each other as they held out 3D cinema glasses, with the arms of the frame pointing at the white desktop screen behind me. They turned the frames, gasped as the polarising lenses suddenly blocked out the light from the screen and then exploded into different directions in the library to get closer to other screens themselves. Soon, some of the more inquisitive also tried out viewing at the live projection screen, the windows, lights and white paper, discovering that the blanking out could only happen at the desktop screens (as these have their own primary polarising filters). Some students collaborated and found that you could also get the darkening effect on lights if you used two sets of glasses/two sets of filters

They were reluctantly dragged back to be still again in a wide circle around the screen. Glasses held at extinction, I slowly lowered an A6 sized rectangle of clear acetate sheet in front of the screen. the hubbub rose again and then got excited when I stuck a piece of Sellotape to the sheet and revealed a range of polarisation colours. From then on the class teacher and I were the focus of a constant stream of students coming back for more and more Sellotape for their own abstract hidden artworks.

This remarkably simple demonstration, of creating colour effects that could only be seen using polarisation filters, filled a good part of 15 minutes. It brought home to me that what seems like a simple everyday technique for many amateur microscopists (and geologists) still had the capability to bring a sense of discovery and wonder to those who saw it for the first time.

You could also tell that the school/teachers had a very positive and supportive nature in working with their young students as the latter were unafraid and open to trying things out and asking questions when they did not understand. Their enthusiasm only had to be curbed when it got too exuberant. Not everyone understood my explanations of polarisation, but they seemed to have come away having learned a new insight or experience of unexpected things you can do with objects they normally take for granted.

The two sessions of 30 students each took over 90 minutes, including talk, demonstration and the practicals. They were topped and tailed by the preparation and packing time in the library. As I was setting up over half an hour, there was a steady flow of students - to the workstations, and to the books. But this was not a reverent or even dull silent area. It was a place to talk about what books a reader might want to go to next after returning the last one, a discussion of preferences.

I found myself pulled in on a conversation as I saw Peter Bunzl's Clockheart and Moonlocket. I'd been drawn into the series after spending my birthday at Leicester Space Centre last November, when there was a simultaneous exhibition of Steampunk. Cogheart struck my eye as a memento to take home and enjoy with my new rocket adorned mug. The paperback versions of the Magyk series was also on the table, with its lovely black and white illustrations.

After the rush of the sessions, the library emptied and I began to pack,  the cheery librarian returned, and now it was the turn of parents and children to come and visit in ones and twos. The microscope stayed on the table, slides and filters were brought out again as the curious came to peer and delight  in what they saw, adult and child alike. The head louse slide was a common denominator for us parents!

Head louse, composite stacked images of 2D panorama

I found myself chatting to a German parent about the books I enjoyed as a child - from Ottfried Preussler to Michael Ende and Cornelia Funke, and recommending animal and vet related books by James Herriot, Gerald Durrell and, on a more fantastical side, the Redwall series.

After Stephen Hawking's death yesterday I also recommended the children series he'd written with daughter Lucy, as I'd enjoyed reading 'George's Secret Key to the Universe' in one go last night in his memory. I found it a much easier and yet scientifically informative read than the highly lauded but seldom finished 'A Brief History of Time'. It had hard facts as a part of the fiction (something done so well by the adult exponent of the hard SciFi genre, Hal Clement, with 'A Mission of Gravity').

The son of the last parent to arrive had been in one of the earlier sessions. His voice carried over as he explained to his amazed mum why a 3D cinema glasses lens could darken a PC screen "It works because there is already a filter on the computer screen!" Subconsciously turning to look at me after he had said it, I gave him a thumbs up across the room.

I left at 5 pm, having extended the STEM activity for a couple of hours, from a hectic full class session to a more calmly paced one to two with a number of parents and children. Tired but positive.