Pink Floyd’s classic album The Dark Side of the Moon was released in 1973 and spent a total of 981 weeks on the Billboard 200 list of top-selling albums in the US. The album is also famous for its iconic cover, which is a very simple depiction of a beam of white light being split into its constituent colours by a prism. But it turns out that this illustration is very much an artistic interpretation of optical refraction – rather than what happens in real life.

In this episode of the Physics World Weekly podcast, the physics teacher Tom Tierney explains how his students analysed the album cover and learned a lot about the physics of refraction and the optical properties of materials. He also talks about how the album cover fits into a long tradition of the incorrect depiction of how prisms bend light – something that may have emerged to make the process easier to visualize.