Experiment: Measuring the Speed of Light

[Klaynos]

Diamond:

Density 3.5-3.53 g/cm³

 

Graphite:

Density 2.09–2.23 g/cm³

 

The opaque one at visible frequencies is the least dense... I picked these two as they are both carbon... So I don't think we could even take a good guess at the refractive index of chocolate for microwaves

[hermanntrude]

Diamond:

Density 3.5-3.53 g/cm³

 

Graphite:

Density 2.09–2.23 g/cm³

 

The opaque one at visible frequencies is the least dense... I picked these two as they are both carbon... So I don't think we could even take a good guess at the refractive index of chocolate for microwaves

 

hmm... well it's written in the textbook i teach from (which was written by a self-important ignorant prick), that when light goes from a less dense to a more dense medium it is refracted away from the normal, because the speed of the light is lowered by different amounts, and vice versa.

 

I'd like to get to the bottom of this, since I have known this textbook to be wrong before, and I need to know where the wrong parts are

[Klaynos]

Another more common example:

 

Glass (fused silica):

2.203g/cm³

Refractive index: 1.459 at 589.29 nm

 

Water:

0.998g/cm³

Refractive index: 1.33393. at the same wavelength

 

So here less dense lower refractive index holds, this seems to be where the problem occurs.

 

Also you get things like if you add salt to water the refractive index goes up.

 

So it is often taught that refractive index is bassed highly on density, but it's only really because the situation that are often taught happen to be true... Most solids have a higher refractive index than liquids, but IIRC this is mostly to do with the bonds than anything else.

[swansont]

hmm... well it's written in the textbook i teach from (which was written by a self-important ignorant prick), that when light goes from a less dense to a more dense medium it is refracted away from the normal, because the speed of the light is lowered by different amounts, and vice versa.

 

I'd like to get to the bottom of this, since I have known this textbook to be wrong before, and I need to know where the wrong parts are

 

It applies to a traveling wave, but it's bent toward the normal if the optical density is higher. It minimizes the time spend in the denser medium while also reaching its target.

[hermanntrude]

toward, yes. I still have to look that one up, and last night i was out of town