measuring the refractive index of glass microspheres

[damienmorton]

I have some samples of ultra-high index glass microspheres.

The microspheres are in various sizes from 50um to 300um, and the refractive index is reportedly 2.4, but I want to confirm this.

The normal way for measuring the refractive index of glass microspheres is to immerse them in an oil of a known index and look at them under a microscope.

Unfortunately, the available oils only go up to roughly 2.1 index.

Wondering if anyone can think of a way of measuring the refractive index of these glass spheres.

 

[brdf]

If your spheres are transparent (no absorption) and if you can find a goniometer to measure the "phase function" of such spheres, you can determine the refractive index from the rainbow angle, see, e.g.:

" Mathematics of the Rainbow"
Mathematics Teacher, v81 n6 p484-88 Sep 1988