When a wave strikes a barrier, it is reflected. For simplicity, we will consider a wave striking a flat barrier. The wave will strike the barrier at a certain angle, and will be reflected at the same angle.
This article is part 1 of the series 'Reflection, Refraction and Diffraction'. Prior knowledge is not required. The link to part 2 of this series is at the foot of this article.
- Whenever we measure a wave being reflected off a barrier, we use an imaginary line Perpendicular (at 90 degrees) to the barrier to measure the angles from. This line is called the Normal.
- The angle of incidence is the angle from the normal that the wave is incident at. It is abbreviated to i
- Using the rule 'the angle of incidence is always equal to the angle of reflection', we can see that the angle of reflection will be the same. The angle of reflection is abbreviated to r.
We measure from the normal rather than the surface to avoid complications. For example, imagine that a wave was being reflected at the very edge of a mirror - you would have no surface to measure from on one side! Also, as we will go on to explore now, the surface may be uneven.
The angle of reflection is still equal to the angle of incidence. Here is what is happening: each wave strikes a particular point on the surface which will have a particular gradient. We can find this gradient by drawing a tangent to the curve (the red line on the diagram above). This is the gradient at the one point on the surface that the wave hits. Now we can apply the same technique as above to find the angle of reflection. This is what is happening on any non-reflective surface, each wave is reflected off at a different angle to the ones nearby because the surface is so uneven - the waves dont just reflect off in random directions.
Next post in series: Refraction of Light
http://exploringgcses.blogspot.com/2012/01/refraction-of-light.html
Next post in series: Refraction of Light
http://exploringgcses.blogspot.com/2012/01/refraction-of-light.html
