17 December 2010 at 14:31 #15367
I first heard about the RGB Auto Colour Changing LED lightbulb on Physics Teaching News & Comment – an e-mail discussion list run by the Institute of Physics. The device is a mains-operated LED bulb that has six red, six green and six blue LEDs inside a translucent envelope. You can’t see the LEDs (at least not in the version I have) and the bulb has a screw thread. There are two versions of this bulb: one that always produces white light and another that scrolls through all of the combinations of the colours that it can produce. The latter shines white, red, green, blue, yellow, magenta and cyan in that order. Each colour shines for about three seconds. One of the very noticeable things about this bulb is the lack of heat that is generated. I had the white bulb on continuously for two hours and it still felt cold to touch. This surprised the pupils too. The most amazing thing about this bulb is the way that it changes the appearance of objects when the colours change. I don’t think I’ve ever seen this demonstration done as effectively as this. I have a coloured periodic table and in the pictures (left) you probably can’t appreciate how effective the colour changes are as it proved difficult to photograph. In the bottom left hand corner, in front of the periodic table, there’s a piece of packaging that has big circles with the printing colours on them (cyan, magenta, yellow and black); these changed like traffic lights as the bulb changed colour. This can be seen to better effect on a short video clip available at http://www.iop.org/Journals/physed. During the course of the lesson in which I used the bulb we also discussed the way that the colour of light affects the appearance of objects in art. This discussion was then followed up by the art teacher, giving the whole lesson a cross-curricular feel. RGB Auto Colour Changing LED 240V BC Lightbulb was available from ultraleds.co.uk. Look for 240 V mains bulbs. Price: £11.50.
(From Physics Education)