In our museum collections is a small leather wallet with what first appears to be a piece of clear framed glass inside. It doesn’t look like much, but this is actually a diffraction grid – used to separate light into it’s component wavelengths – think something along the lines of Pink Floyd’s Dark Side of the Moon album cover.
They work by having thousands of tiny ruled lines etched into the surface allowing the light to bounce off dramatically. They are used in a lot of different fields – including light analysis and laser optics.
Our particular grating is from the early 1900s and has 14,400 lines per inch meaning we get a stunning display of rainbows when light is viewed through it. Volunteer Angharad @amjones_art and I took the opportunity of some early March sunshine to walk around campus and take photographs through the lens on a smartphone – the results speak for themselves!