Hello, i have a question.
How works a PL mount adapter for a PMW-EX3? Can i use normal 35mm Arri PL mount film lenses on a PMW-EX3?

No.
-C

Well, if someone is making an PL adapter I am pretty convinced that you can attach a PL lens to it. What you will not get though with the combination is the angle of view or the depth of field of the 35mm camera. The lens will be way much more tele than with the 35mm camera and your depth of field will remain pretty much the same as with the original lens. The small "film gate" of the 1/2" is to blame for this.

So, I would say yes. Just be aware of the points above.

mika