The optical radiation efficiency (), the ratio of scattering cross-section to extinction cross-section, of spherical metal nanoparticles (M Al, Ag, Au and Cu) surrounded by glass and water was calculated using classical electrostatics. The effect of varying particle diameter (similar to 100 nm) on was also studied for free space wavelengths in the range of 400-1200 nm. The variations in the value of with the diameter () of the metal nanoparticles were calculated on the basis of quasi-static approximation. The increases with the size of metal nanoparticles. Corresponding to a metal nanoparticle, was found to exhibit a sharp dip ( (dip)) at a characteristic wavelength ( )(M) in a particular medium ( = air, glass and water). ( )(M) was independent of particle size. The ( (medium))(M) was found to be slightly blue shifted for all metal nanoparticles surrounded by glass or water with respect to those in the air.