Liquid Crystal Discussion
I quite often find that the simple explanations necessary to answer IB questions aren't quite enough to answer students questions in class. Today we were talking about how the LCD works. The liquid crystal rotates the plane of polarisation allowing the light to pass through crossed polarisers, when a pd is applied the plane is no longer rotated and the light can not pass. All well and good for explaining how a simple 7 segment watch display works but what about a colour computer screen? Well that has 3 coloured segments so by combining red green and blue you can get different colours. What about all the different shades? Now we need more information. The vital thing is that by changing the pd you get different angles of rotation so can vary the intensity of light passing through the pixel. Looking at the photo of a pixel from my TV it may also be possible to illuminate different bars in each colour pixel. Not sure if that happens or not so I'm going to have to watch more TV to find out. It's probably good that the new syllabus doesn't include too much "new technology", it has the habit of becoming obsolete very quickly.