Period Costs. Period costs are expenses that are easier to attribute to times and accounting periods than actual production processes or finished goods. Typically, managerial accountant want to classify expenses in categories that can improve operations. Manufactures tend to focus on functional classifications.
The amber color of these impact-resistant polycarbonate lenses block short-wavelength blue light and 100% of ultraviolet (UV) light, thus providing additional protection against cataract formation and the development of macular degeneration, while increasing contrast on both sunny and bright hazy days.
While copper lenses block blue light better than the other lenses mentioned, they may be too dark for many to wear inside. Yellow/amber, orange and brown/bronze lenses still block enough blue light without the dimming effect to still produce some of the same benefits mentioned above.