In support of all the students who are displaced from school due to the Corona virus. Access to physics zone and chemistry zone lessons are now available free of charge. This will be maintained at least through August 1st 2020. Learn and be well.

 Physics Lessons Review Links Solutions Physics Shop

# Image Formation - Ray Tracing Basics

 Wherever two or more light rays from the same point on an object cross or seem to cross, an image gets formed.  For any given mirror or lens, you could pick any two rays from your object (the thing we are making the image of) and trace them out using a protractor and possibly some trig.  It turns out, that there are three rays that we can be absolutely sure of without the use of a protractor.  Drawing any two of these known rays can identify where the image is.  Pick whichever two rays make the most sense to you. Any ray coming in parallel to the principal axis will reflect (if it's a mirror) or refract (if it's a lens) through the focal point (or as though it came from the virtual focus).  Keep your wits about you, light bounces off mirrors and passes through lenses. Any ray coming through the focal point (or seeming to pass through the virtual focus) will reflect or refract parallel to the principal axis. Any ray passing through the center of a mirror will reflect off following the law of reflection.  Any ray passing through the center of a lens will pass straight through without seeming to change direction. To find the where the image of an object gets formed, pick your two favorite rays and trace them for the top of the object.  Where the two reflected or refracted rays cross or seem to cross is where the image of the top of the object is formed.  Repeat the process for the bottom of the object to identify where the bottom of the image is formed.  Once you know where the bottom and the top is, the rest of the image is between the them.