1-2” -  The source we used was the Handbook of Laser Therapy by Michael Hamblin (our CSO). It offers a model for how light reflects through different materials (e.g. bone, blood, soft tissue).  But, this model has many variables and the best way to determine penetration is to measure it.    Below is a link to a video showing the penetration of the Luma through the hand.  This is a simple model to show how that light can reach the target tissue of a patient.   https://youtu.be/QnFVxOtCX60