A twenty seven (27) milliwatt LASER is being used in surgery. An inexperienced physician inadvertently directs the LASER at a nearby wall that is 4.1 meters away. If the emergent beam diameter is 1.1 cm, the beam divergence is 1.3 milliradians, what is the diameter of the beam on the wall (and hopefully not in an unprotected eye)?
What is the beam irradiance at the wall?