Refractions in decanter stoppers

Desperate. Me? Possibly. But I've always liked refractions. The sunshine this morning splattered rainbows around the bedroom. 

I particularly liked being shown a diffraction grating in a physics lesson at school, in the mid sixties, which became somewhat synonymous with the light shows that I liked a couple a year or two later. The first one I saw was displayed over The Move at The Marquee club in 1966, when their support act were the Pink Floyd. They knew their place. Syd Barrett stood out even then.