Maybe its index of refraction is a little higher, and that would be why.

As the density changes, so does the index of refraction.

Young did not use a symbol for the index of refraction, in 1807.

Typical oils used have an index of refraction around 1.515.

Glycerin has almost the same index of refraction as glass.

Color and optical refraction index do not matter to electrons.

The ultrasound waves create changes in the air's index of refraction.

The slow ray is the one for which the material has the highest effective refraction index.

Red has a smaller index of refraction than blue.

"Glass with the same index of refraction as air," he said to himself, in his own voice, though he did not do the talking.