If the particle is situated at the middle of the beam, then particular person rays of mild are refracting by way of the particle symmetrically, leading to no web lateral power. The web force in this case is alongside the axial course of the lure, which cancels out the scattering pressure of the laser mild. The cancellation of this axial gradient pressure with the scattering pressure is what causes the bead to be stably trapped slightly downstream of the beam waist. In cases the place the diameter of a trapped particle is significantly smaller than the wavelength of mild, the