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Standard transmission

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Standard transmission diagram
The optical transmission for any chosen standard sample thickness is calculated from the measured transmission of a sample of known thickness, as well as the surface losses. The internal transmission and the total transmission (including surface losses) for the thickness of interest are given.
Measured transmission
Known thickness
Surface losses
Thickness of interest

Internal transmission
Total transmission
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Surface losses are mostly due to reflection, and depend on the refractive index of the material. For uncoated materials, aliphatic resins give ~6% total reflective losses, glass gives ~8% losses, and polycarbonate gives ~10% losses. Exact reflection intensities may be calculated by the reflection calc. Reflective losses are wavelength-dependant.
Internal losses may arise from absorption or scattering.