On Thu, 24 Aug 1995, Guy Cox wrote: > The beam diameter, assuming that your specimen is in a mountant > of refactive index 1.515, will be an Airy disk at the point of focus, > since the laser source should approximate to a point. > > Thus the radius (centre to 1st minimum) will be > 0.61 * lambda / NA = 0.61 * 488 / 1.4 = 213nm > for the 488nm line. also assuming the BFP of the lens is 100% filled. Regards, ****************************************************************************** Stamatis Pagakis University Laboratory of Physiology [log in to unmask] University of Oxford, Parks Rd. FAX: +44 (0)1865 272469 Oxford OX1 3PT, United Kingdom Tel: +44 (0)1865 272551