Whispering-gallery wave Whispering-gallery wave Whispering-gallery waves, or whispering-gallery modes, are a type of wave that can travel around a concave surface. Originally discovered for sound waves in the whispering gallery of St Paul’s Cathedral, they can exist for light and for other waves, with important applications in nondestructive testing, lasing, cooling and sensing, as well as in astronomy. Whispering-gallery waves were first explained for the case of St Paul's Cathedral circa 1878 by Lord Rayleigh, who revised a previous misconception that whispers could be heard across the dome but not at any intermediate position. He explained the phenomenon of travelling whispers with
National Portrait Gallery, London In 2012, the Gallery licensed 53,000 low-resolution images under a Creative Commons licence, making them available free of charge for non–commercial use. A further 87,000 high-resolution images are available for academic use under the Gallery's own licence that invites donations in return; previously, the Gallery charged for high-resolution images. , 100,000 images, around a third of the Gallery's collection, had been digitised. National Portrait Gallery, London The National Portrait Gallery (NPG) is an art gallery in London housing a collection of portraits of historically important and famous British people. It was the first portrait gallery in the world when it