Question

I want some trick to learn the Ray diagrams and solve the problems on it

Answer 1

honestly, this is one of the few topics I recommend just memorizing the rules. It mostly shows up as a discrete with a very common answer structure.. so you can get away with just knowing the rules/tricks and not fully understanding ray diagrams. Of course, this can backfire if you get an optics passage but even then, you should be okay.

converging:
1) the object is located beyond the radius of curvature (R)- SIR (smaller, inverted, real)
2) the object is located at R- SSIR (same size, inverted, real)
3) the object is located between R and F- LIR (larger, inverted, real)
4) the object is located at F- no image is formed
5) the object is located between F and the mirror- LUV (larger, upright, virtual)

diverging:
always SUV (smaller, upright, virtual)


from there, you just need to know the sign conventions so you can figure out which side of the mirror/lens the object/image is on, etc. You can also relate the size relationship to the image location (larger = farther out, etc.).

That really should take care of 90% of optics questions and is a quick memorization. It's best to memorize as little as possible but here is a situation where I'd say go for it.