Which describes how outer space, air, and glass affect the speed of light?

Question

anonymous · Answer

A.
	Light travels fastest through outer space, it travels somewhat slower though air, and of these three, it travels the slowest through glass.
	
 
B.
	Light travels fastest through glass, it travels somewhat slower though outer space and of these three, it travels the slowest through air.
	
 
C.
	Light travels fastest through glass, it travels somewhat slower though air and of these three, it travels the slowest through outer space.
	
 
D.
	Light travels fastest through air, it travels somewhat slower though glass and of these three, it travels the slowest through outer space.

abhisar · Answer

A

colouringme · Answer

Basically you need to know the value of n (refractive index) of each. The greater the value, the slower the speed of light going pass through it. 

From equation :
$$v = \frac{ c }{ n }$$

where v is the speed
c is the speed of light in vacuum  and n is the refractive index