Steam from a hot cup of coffee is just a mini cloud. It lets us do experiments that are not easy on the big ones in the sky.
Here we see directly that iridescent cloud colours are not the filmy continua they seem.
Instead, individual droplets diffract light to send colours to the eye or camera.
Droplets of similar size in small (angular) regions each diffract the same colour towards us. Here we are privileged to see not the droplets – they are much too small – but their individual light. We see stars similarly even though their disks are much too small for our eyes to resolve them. |
