I'm working in the area of near-infrared spectroscopy where we shine light through tissue and measure the attenuation at a detector nearby. The detector is actually placed on the same surface as the emitter (ex. both on the head about 4cm appart) so rather than the standard Beer-Lambert model, the "modified" Beer-Lambert model for scattering media is typically used. One thing I've noticed is that changes in the concentrations of chromophores in the tissue (ex. induced by the heartbeat) tend to be associated with a larger change in the detected light when the light is driven at a higher wattage. Is this expected given the physics of scattering/absorption?