The important topics are:
>Electrostatics and Magnetism (Moderate toughness, covering almost the entire first book, you need to go through it sincerely as many new concepts are being introduced).
> Ray Optics (It is quite easy, not much different from what you studied in X and weightage in Boards is quite high).
> Wave Optics (Easy, but completely new. You need to understand the concepts of double slit expt., interference, diffraction and polarisation).
>Modern Physics (A really easy one due to the fact that you studied most of it in XI Chemistry)
>Semiconductors (I personally believe some parts of this topic to be on tougher side as we were taught this in a real haste during our JEE Preparation and hence concepts were never pretty clear. Nevertheless, if you give it just 4-5 hours, it will just get perfect)
>EM Waves and Communication(U need to memorize several things which gets really boring at times)