Lighting suggestions

I have a 10 gallon reef aquarium that is 20 x 10 x 12 which is housing live rock and orange mushroom corals with a clown fish that I am looking for an LED light for. I was thinking about a par38 bulb but I was not sure if that would cover the entire tank without shadows. I now have a light that is right on top of the tank but I would like to get something that is raised up over the tank.

If a par38 bulb is okay for the tank what lumens would I need for it to be.

Thanks,