This video shows the trapping efficiencies as a function of the incident angle for a ray impinging on a spherical particle (glass, refractive index: np = 1.50) in water (nm = 1.33). On the right side the scattering process as a function of the incident angle is represented, on the left side the calculated scattering, gradient and total trapping efficiency.
Agnese Callegari, Mite Mijalkov, A. Burak Gököz, and Giovanni Volpe, “Computational toolbox for optical tweezers in geometrical optics,” J. Opt. Soc. Am. B 32, B11-B19 (2015). http://dx.doi.org/10.1364/JOSAB.32.000B11
Brownian motion in an optical trap (low NA).
Brownian motion in an optical trap (medium NA).
Brownian motion in an optical trap (high NA).
Scattering of a ray on a spherical particle (high refractive index).
Scattering of a ray on a spherical particle (low refractive index).