1. The problem statement, all variables and given/known data The laser beam is not a point source. It is known that it has a rectangular shape with a divergence of 30 mrad x 1 mrad. I would like to know how large my laser lobe will be at a distance of 250 mm from the laser source. 2. Relevant equations I think you can use trigonometri for a triangle. tan(A) = opposite/adjacent 3. The attempt at a solution The angle of the rectangle will be half of angle of the divergence spread since the divergence is linear. opposite = adjacent * tan(A), thus opposite_height = 250 mm * tan(15mrad) = 3.75 mm opposite_width = 250 mm * tan(15mrad) = 0.125 mm Thus, the laser beam or lobe should have the size of 2*3.75 mm x 2*0.125 mm = 7.5 mm x 0.25 mm at a distance of 250 mm from laser source. Correct?