Sachin Sarkar: "What proof need to collect to proove false 498A".
There cannot be any proof or evidence for non-existence of something. If the wife makes a complaint saying that her husband was having an affair with a girl, she will have to give evidence. But the question of evidence will come only after the matter goes to court. Well before that your friend would have been arrested, detained in custody and released. Thereafter there will be long court battle. Ultimately your friend may be acquitted for lack of evidence after months or years. But before that all women in the neighborhood would have turned hostile towards him. They may influence their husbands too. If your friend is staying in a colony or quarters, he will feel rightly or wrongly that his neighbors were murmuring behind his back. Of course you and other friends of your friend may congratulate him for successfully developing a relationship with a pretty girl and for having a jolly good time. Thus your friend will have two sides one nightmarish and the other exciting. Whether he would prefer your praise and the good times with the other girl or not, his marriage would have been lost once and for all.
If he wants to save his marriage let him sit down and talk it over with his wife. Let him find out from his wife what exactly she wants him to do. It may be that she may want him to cut off all relations with the other girl. Or she may agree to a limited friendship with the other girl with certain dos and don'ts. But if he is (you are) thinking in terms of proofs and evidences take it from me the marriage has ended. Has your friend got children?
I am writing this after seeing similar cases. I am not expressing any opinion of my own in this matter. It will be thrilling and exciting to have an extra-marital relationship. But if one gets into it peace of mind would be lost forever.