Reflected light from a soap bubble, 1912.
© Science Museum / Science & Society Picture Library
Colour illustration taken from 'Soap Bubbles' (1912) by Charles Vernon Boys. This chart shows the colours that are 'present in the reflected light from a soap bubble, of any thicknes from nothing up to 50 millionth of an inch, if the light strikes and is reflected from the bubble perpendicularly or nearly so'. Charles Vernon Boys (1855-1944) was an English physicist who designed a calorimeter for determining the calorific value of coal gas. He was also President of the Physical Society from 1916-1918.