I you have arrived this far, then solving this souldn't be a problem!
I THINK you must try each of those 2 light switches and the button.
The button wont be difficult to press.
To power the left light switch, you can simply fall down (from first screen to second) and, as you fall, instanly fire the beam.
I think you can do that eve for second (right) light switch, but I don't think that's the solution. I think the solution is to climp up the rope up to the top, and then simply press right arrow key to arrive on that block on first screen. From that block you (just like before) fall down to the right screen on the conveior belt.....
Hope you get it, because if you didn't, I will have to play that game anew!
LOL