Portrait of the English physicist, physiologist and Egyptologist Thomas Young, 1773-1829. Young studied medicine and published experiments showing that change of focus of the eye is a result of the change in curvature of the lens. He later devised the three-colour theory of human colour vision. He experimented with light interference and diffraction. He explained the effects using a transverse wave theory of light rather than the particle theory which was influential at the time. He also measured the wavelength of light, worked on surface tension and elasticity and contributed to the interpretation of the ancient Egyptian hieroglyphics on the Rosetta stone.