In this paper, optical properties of Au–Ag spherical nanoalloy are investigated by means of Generalized Lorenz–Mie Theory (GLMT) when this nanoparticle is embedded into water. Scattering, extinction and absorption cross-sections of this nanoalloy into water are calculated by changes of incident wavelengths in visible and near infra-red region. Moreover, changes of height and wavelengths of exti...