This video shows the rays wch are used in drawing the ray diagrams for the lenses. Infact this video uses three rays to help us locate the image with the help of the ray diagram:
(i) One wch travels parallel to the pricipal axis after refraction passes through the principal focus,
(ii) One wch travels thru the optical center goes undeviated, and
(iii) Ray passing thru principal focus after refraction goes parallel to the principal axis.
Aid to ur memory (P, C, F)
This particular video shows the rays used for image location in case of concave lenses, still they are the same P, C and F.
But in fact in real practise I always prefer to use the first two rays for locating any image :)
The different image located for different position of the object is shown below: (Probably this u all hav done at class Xth level)....
But just for ur revision I discuss in the class....
