if you put your bulb across the top and your basking bulb near by the uvb, then you can ensure yourself that your chameleon is getting uvb and uva at the same time. There are some lights that are combo uva/uvb. 11 inches is far enough away that your chameleon will not rub on the screen and get burned where the basking light is. I was just asking having it 11 inches away what your basking temp was? Sometimes if you have it too far away it is not warm enough, but that would depend on the wattage of your bulb also. that is why you need to measure your temps and see what they are.