The transmissivity T of a transparent material 20 mm thick to normally incident light is 0.85. If the index of refraction of this material is 1.4, compute the thickness of material that will yield a transmissivity of 0.75. All reflection losses should be considered. Transmissivity T is a ratio of intensity (I) of the light going out of the material to that (lo) of the incident light.

The transmissivity T of a transparent material 20 mm thick to normally incident light is 0.85. If the index of refraction of this material is 1.4, compute the thickness of material that will yield a transmissivity of 0.75. All reflection losses should be considered. Transmissivity T is a ratio of intensity (I) of the light going out of the material to that (lo) of the incident light.