I have a doubt plzzzz reply as fast as possible ..i had a doubt in physics lesson light that when we are drawing a r ay diagram of object placed at f should we use any specific rule or we can use rules which are convienient to us plz reply fast i have my exam on tuesday



There are three rules for drawing ray diagrams right we can use the laws which are applicable for it and you need to know where the object image is formed by the mirror so that you can use the rules and draw ray diagrams conveniently but remember that you should know where the image is formed by that we can draw ray diagrams once try this and check you ray diagrams and the ray diagrams in the text book  once refer the ray diagrams before drawing them
hope it helps thank you!!!!!
When incident ray is parallel reflected ray passes through f and vice versa
when incident ray passes through C reflected ray traces the same path. 
So the rules for obj at f are when the incident ray passes through the C it traces the same path & when the incident ra is parallel the reflected ray passes through the focus