Audultery

I am not an advocate but here are my thoughts (as I too have successfully defended a DV case sans advocate):

First, adultery was not committed by her but by the person who she is having an affair with. See Section 497 of Indian Penal Code. Adultery expressly requires a s*xual intercourse and I would think that would be hard to get evidence. The photos that you may have may prove that she was not loyal, having an affair, etc. which suffices to get you divorce. I think that you will have to get it on grounds of mental cruelty to you if you have evidence that she was having an affair.  This in turn will disentitle her to any maintenance. 

Now lets come to evidence... To prove your evidence, you will have to file an affidavit from the person who took the photos along with an application to call him as a witness. Then you should  cross-examine him.  Show the photos to him while he is in the witness box. Mark them as exhibits. This cross-examination and the transcriptt of the cross-examination along with the photos then can be used by you in other proceedings, for example, in the Family Court. You may not have to get the witness cross-examined again in other Courts. 

Once the evidence is in, then, you should file your application to seek any relief you want. 

Good Luck!

Check this link: https://www.lawyersclubindia.com/forum/Infidelity-over-phone-is-a-ground-for-divorce-87755.asp#.UiTfKtJHIhw