凸透鏡成像問題

If you are given an arbitrary ray AB, as shown in the following diagram:


圖片參考：http://imgcld.yimg.com/8/n/HA00458726/o/20130414215725.jpg


(1) Draw a construction ray CD parallel to AB
(2) CD would meet the focal plane (焦平面) at point E
(3) Join BE and extend the ray, this gives you the required refracted ray (折射線)


2013-04-14 23:35:57 補充：
Q:係咪一定要係同一點定係同係係焦平面
A: Any two parallel rays must meet at the focal plane after refraction by a convex lens. The construction ray (the green dotted line ) that passes through the lens centre just represents a parallel incident ray.

use the lens formula 1/u+1/v = 1/f