The concept of Optical Path Length (OPL) is important for accurately describing how light propagates through materials. OPL is a way of measuring the effective distance light travels, accounting for any changes in speed due to the medium. This is particularly relevant when light passes through substances like glass, which alters both its speed and path.
In simple terms, the OPL is the distance light would have traveled in a vacuum instead of the medium it actually traverses. It takes into account the medium's refractive index, using the relation:
- \( ext{OPL} = n \times d \)
where \( n \) is the index of refraction and \( d \) is the physical distance.
In the given problem, the OPL is the distance the microscope lens had to adjust to shift focus, totaling 2.10 mm when measuring the perceived optical path through the glass. The refractive index helps translate this optical path into understanding how thick the material truly is and how significantly it altered the light's trajectory. Thus, the OPL gives insights into both the medium's properties and the adjustments needed for optical devices to maintain clear images.