In this paper, the optical properties of gold nanoparticles investigated. For this purpose the scattering intensity of a laser beam incident on gold nanoparticles has been studied using Mie theory and their respective curves versus different parameters such as scattering angle, wavelength of the laser beam and the size of gold nanoparticles are plotted. Investigating and comparison of the depicted plots show that the scattering intensity increases with increasing gold nanoparticles size up to 100 nm and further increasing of nanoprticles sizes leads to oscillating like behavior in the intensity patterns. Several peaks emerges in the patterns of intensity versus nanoparticle size. It was also found that for particles with sizes less than 100 nm the intensity patterns versus wavelength had a one peak about 520 nm while for the particles bigger than 100 nm there appears other maxima in different wavelength too. Changing the angle of scattering led to change in the intensity pattern of scattered light and its minimum value was detected at 90°. These results can be used in detecting cancerous tumors and in cancer therappy. تفاصيل المقالة