# [Bf-committers] ior

Ivan Sedo ikoframe at zoznam.sk
Sun Apr 3 13:51:39 CEST 2005

```indeed it is not negative, if one ior was i_1 than for the opposite
direction the ior is i_2 = 1/i_1

it comes out from senll's law

ivan

On Sun, 2005-04-03 at 12:56 +0200, Frédéric van der Essen wrote:
> Of course it can !
> the ior isn't lightspeed_in_void / Lightspeed_in_material !!!
> this is the special case of an object standing in void.
>
> the real formula = lightspeed_in_first_material /
> Lightspeed_in_second_material.
>
> if the light goes slower in the first than in the second, then the ior
> is smaller than one.
>
> in the case of a bubble in water, the lightspeed is slower in the water
> than in the air, so the ior is negative when the light
> enters the bubble, and positive when the light goes out the bubble.
>
>
> Daniel Barbeau wrote:
>
> >ior_of_material  = Lightspeed_in_void /  Lightspeed_in_material
> >
> >Lightspeed_in_void is light's maximum speed. 300 000 km/sec If i
> >recall well.
> >
> >Lightspeed_in_material can't be higher than Lightspeed_in_void, so
> >ior_of_material can't be lower than 1.
> >
> >I guess this could be an Elysiun question and an Elysiun answer.
> >
> >Dani
> >
> >_______________________________________________
> >Bf-committers mailing list
> >Bf-committers at projects.blender.org
> >http://projects.blender.org/mailman/listinfo/bf-committers
> >
> >
> >
>
> _______________________________________________
> Bf-committers mailing list
> Bf-committers at projects.blender.org
> http://projects.blender.org/mailman/listinfo/bf-committers

```