Rainbow Making - Cup and Small Mirror

Inspired by the Unnatural Nature project I found, I decided to try to make my own rainbow. I visualise a final display with a big rainbow over one wall with a backdrop photo. I started off with a glass of water and a small mirror and a small but very bright LED torch. This didn't work as the torch light wasn't a slim enough beam and the glass and mirror should have been bigger. I used black card to reduce the torch light to a tiny beam and then managed to get a tiny rainbow.