Photoacoustic effect a rotating slotted wheel. He noticed that the resulting acoustic signal was dependent on the type of the material and correctly reasoned that the effect was caused by the absorbed light energy, which subsequently heats the sample. Later Bell showed that materials exposed to the non-visible (ultra-violet and infra-red) portions of the solar spectrum can also produce sounds and invented a device, which he called "spectrophone", to apply this effect for spectral identification of materials. Bell himself and later John Tyndall and Wilhelm Röntgen extended these experiments, demonstrating the same effect in liquids and gases. However, the results were too
In the House of Stone and Light (album) As stated in the EPK, "Shape the Invisible" is Page's favorite on his debut album. As described by him in his video EPK: "My favorite song is 'Shape the Invisible', purely because of what the lyrics say. I was reading a book about Leonardo DaVinci and he mentioned that this shape the invisible in a sentence, and I thought what a great title. And at the time I wrote the song, there is as there always is trouble in the world, and I really wrote it as a wish song." Also stated in the EPK by Page, about the song