Changing interests after joining grad school I joined graduate school in the US with interests in theoretical chemistry/chemical physics. Though I was enrolled for a PhD in chemistry, I was taking classes in physics for an entire year. This made me realize that I was more interested in physics related research than my current work in theoretical chemistry. While I was still in a dilemma, I convinced myself that I should continue in chemistry and joined my current advisor's group. Things were going fine for a while until I ended up having a minor confrontation with my advisor that made me feel sick about myself. I didn't know some of the basic things he was asking me and I was left stupefied by him. This made me think if I really wanted to pursue research in this direction. As a reaction to the flashpoint I had hit, I approached another professor in the physics department. While he rejected my request, he also notified my current advisor about my intentions. I really didn't mean to hurt my current advisors' feelings about this but, I was dumbstruck when he confronted me about my emails to another professor and accused me of unethical behavior. I am really confused about what to do with my situation. There have been a few students who have had similar issues of feeling disconnected from their research in my current research group, in a case even one of them switched to another group abruptly. 

What should I do if my current advisor decides to step down?

Edit

How do I really find out what I am passionate about and is there a way to separate the reality from noise?
Things were said between the two professors that you couldn't control. It puts you in a difficult position, but might also be an opportunity. 

To switch fields you need to satisfy the university about some things, but also find an advisor in the new field. Either of these could be a stumbling block. The worst case, I think is that you need to find a new university, but that isn't entirely uncommon. It would cost you a bit of time, of course. 

But there is little worse than spending your life doing things that don't interest you. There is no replay button on life. 

Re-evaluate both your desires and your options. But also connect to those at the current university who see you in a positive light. They can also give you advice. 

FWIW, I think your advisor behaved badly in making accusations against you. I don't see your explorations as unethical in any way.