Which describes a substance with a high index of refraction?

a) It bends light less than air.

b) It causes light to slow down significantly.

c) It causes light to speed up significantly.

Question

Which describes a substance with a high index of refraction?
 	
a)	It bends light less than air.

b)	It causes light to slow down significantly.

c)	It causes light to speed up significantly.

osprey · Answer

b) It causes light to slow down significantly.

osprey · Answer

refractive index is defined as the speed of light in a vacuum divided by the speed of light in a medium.
the speed of light in a vacuum is always the same at 300,000,000 metres per second. Nothing, it seems, can travel faster than that speed. So the speed of light in any medium must be lower than that of light in a vacuum 
Hence the refractive index of materials will be greater than one.