Hey Ankit,

You can apply for Airforce after graduation. There's a national level exam known as Afcat for Airforce. The eligibility criteria is B.Tech/BE from any recognised university or any degree from a recognised university with Physics and Maths in +2. 

But since you're from Arts, you can apply only through special entries like logistics and management but for that you are asked to complete your post grad or MBA.

Hope it helps you, good luck!