Light : Type of Medium For the Propagation of Light
Light travels along a straight line. The path of light changes only when the medium changes or when it's strikes with any other surface.
Transparent Medium:
A medium which allow the passage of light through it freely is known as a transparent Medium . Example : Water , Glass and Glycerin are Transparent.
Opaque Medium :
A medium that blocks light from travelling through it is called opaque. Example : wood , metals , bricks .
Translucent Medium :
A medium in which light can travel partially, but it's intensity reduces rapidly are called translucent. Example : oil