From: '''newspam'''@nonad.co.uk   
      
   On 07/01/2026 12:03, Jeroen Belleman wrote:   
   > On 1/7/26 12:54, Martin Brown wrote:   
   >>   
   > There are pretty decent polarizer sheets in LCD screens. Using   
   > these, I discovered that certain Chinese brands of polyester   
   > rulers make fair quarter-wave plates. Build your own quantum   
   > optics experiments for free!   
      
   One of the cuter physics demos with polarisers is to create an image in   
   clear Sellotape on an OHP slide and then cross them to do the reveal.   
      
   You have to calibrate your choice of tape and number of layers.   
      
   I used a child's drawing of a house.   
      
   In the bad old days long before thin film deposition they used to make   
   research grade H-alpha filters out of a stack of layers optically clear   
   calcite crystals and highly polished optically flat quartz wave plates.   
      
   They were very difficult to make and horrendously expensive!   
      
   --   
   Martin Brown   
      
   --- SoupGate-DOS v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)