An effect that combines both refraction and reflection is
total internal reflection. Consider light coming from a dense
medium like water into a less dense medium like air.
Total internal reflection
Refraction of light from water into air
When the light coming from the water strikes the surface, part will be
reflected and part will be refracted. Measured with respect to the normal
line perpendicular to the surface, the reflected light comes off
at an angle equal to that at which it entered at, while that for the
refracted light is larger than the incident angle. In fact the greater
the incident angle, the more the refracted light bends away from the
Thus, increasing the
angle of incidence from path ``1'' to ``2'' will eventually reach a point
where the refracted angle is 90o, at which point the light
appears to emerge along the surface between the water and air. If the
angle of incidence is increased further, the refracted light cannot
leave the water. It gets completely reflected. The interesting thing
about total internal reflection is that it really is total. That is 100% of the light gets reflected back into the
more dense medium, as long as the angle at which it is incident to the
surface is large enough.
Fiber optics uses this property of light to keep light beams
focussed without significant loss.
Fiber optic cable
The light enters the glass cable, and as long as the bending is not too
sudden, will be totally internally reflected when it hits the sides, and
thus is guided along the cable. This is used in telephone and cable
TV cables to carry the signals. Light as an information carrier is
much faster and more efficient than electrons in an electric
current. Also, since light rays don't interact with each other
(whereas electrons interact via their electric charge), it is possible
to pack a large number of different light signals into the same fibre
optics cable without distortion.
You are probably most familiar with fibre optics cables in novelty items consisting of thin, multi-coloured strands
of glass which carry light beams.