# Thread: Transmittance of light on the ophthalmic lenses

1. ## Transmittance of light on the ophthalmic lenses

Goodevening from Athens (Greece).
Now I am studying the properties of the ophthalmic lenses (nontinted), and I can't find a mathematical function for the that property. From the Geometrical Optics is noted the relation:
(transmission %+reflection%+absorption%=100%, for non monochromatic sources).
Also a refference to the international bibliography will be very useful

Thank you very much in advance

P.S Because my english are not good and my expression is not right please notice me if you can't understand what I am asking.
Sh.K

2. The initial amount of light you should assume to be 100% then you loose a percentage to reflectance at the first surface, the remaining percentage is used in the following formula where the absorption reduces that percentage even further, then the last surface will reflect light away so you will need to plug the remaining percentage back through the reflectance formula, the final percentage is what is remaining upon exiting the lens. This percentage can be used to compute the quantity of light remaining compared to the quantity entering the lens.

For Reflectance your percentage is going to be:

Ir = Percentage of reflected light (%)
ni = Index of the incident material
nm = Index of the material

$I_r = 100*\frac{(n_m - n_i)^2}{(n_m + n_i)^2}$

For Absorption your percentage is going to be:

It = Transmission through lens (%)
Ie = Light entering lens (%)
T = Transmission per 2mm of lens material
q = Thickness of lens (mm)

$I_t = 100*I_e*(T)^{\frac{q}{2}}$

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