Diffraction

Diffraction in the process of waves spreding out after having passed a barrier. The extent to which waves diffract relies upon the width of the gap in comparison to the wavelength of the wave. Diffraction is a useful property to understand when studying the comparative properties of short-wave and long-wave radio communication.
Physics - Waves - Reflection, Refraction and Diffraction


This article is part 4 of the series 'Reflection, Refraction and Diffraction'. Prior knowledge may be required. If you have difficulty with this article, read its precursor here: http://exploringgcses.blogspot.com/2012/01/total-internal-reflection.html

In order to understand this fully, consider a wave that starts from one central point and radiates out. It will radiate in all directions. The waves in this article should be considered as many of these placed directly next to each other, moving forwards. Each one will radiate to the right and left, but this will be counteracted by the opposite movement of the areas right next to them, so the wave moves in a straight line forward.

When the wave passes the barrier, the very edge of it has no wave to the side of it. This means that nothing is preventing it from radiating to the side as well as forwards. This leads to the wave's edges spreading out in a circular way from the edge of the wave's main body. This diagram should illustrate the principle:

It is not neccessary for there to be two barriers and a gap: diffraction would also happen if a wave were to pass and be partially cut off by one barrier.


When the width of the aperture is equal to the wavelength, there are no pieces of the wave 'sandwiched', so all of the waves have been diffracted and there are no straight parts. Diffraction is a property shown by all waves.


This is the last of 4 articles in the series 'Reflection, Refraction and Diffraction' under the topic 'Waves' in Physics