Catching a rainbow

While in the pub and building cereal box spectrometers last Friday I thought I would create a semi permanent attachment for my iPhone so I could show someone a spectrum of light wherever and whenever I felt the need to wow someone with SCIENCE!!

I have taped a piece of DVD transmission grating onto my iPhone. Without the slit you can aim the camera at something dark (usually I face it at my hand) and then over the top of that aim the camera at the light source. The light then travels to the DVD grating which is one half of a snapped in half, the side without the reflective coating. As the camera is pointing in a different direction than the light you can get an eerie floating spectrum that you can interact with which is how I took the picture of me holding the spectrum between my fingers.