Visible – use an ohp to give a big spectrum (see slide 11). Use a security camera to show infrared. Put IR transmitting plastic over the ohp and see the IR part only on the screen. Also use the camera to show remote controls working.
Security camera ~ £30 from Argos – http://www.argos.co.uk. Black perspex seems to be an IR transmitter but floppy discs (the actual disc bit inside) are supposed to work too.
These camera’s give a black and white image and have a microphone. They plug straight into a TV with a SCART socket. Having set up the big spectrum get a pupil to point to the outermost red part of the spectrum, right on its very edge. Then using the camera and TV you can show that there is something past this – an inch or so wide band – IR. Next put the IR transmitting plastic on the ohp. The visible spectrum should disappear and only a band of IR will be visible on the TV screen.
Remote controls will also show up as will IR ports on PDA’s and laptops.
The TV and camera can also be used to magnify meter readings allowing a class to see for themselves.