Thursday 3 March 2011

Light can be bent... (Sort of.)

Diffraction is the bending of waves around an object in its path. This is due to how it spreads out from the source, not in straight lines, but in curved waves. Light is a wave, so in effect it does bend.

When waves reach a narrow slit, the wave in the slit vibrates like a point source. The waves thus sent out from secondary sources along the slit are nearly in-phase when arriving any point in the forward direction. The diffracted wave resembles a circularwave with centre at the slit.

The amount of diffraction depends on the wavelength and the size of the object that the wave hits. Waves with a larger wavelength diffract more, and smaller wavelegnths diffract less.
An example of this is your shadow. Shadows aren't sharp images; they are fuzzy around the edges, which is due to diffraction. As the rays hit you, the waves bend around you and then continue on, but they have been changed, and so the image projected on the ground is no longer sharp.

Sound also travels around corners because of it. Lower frequency sound waves diffract better.Light does not diffract well, as it has a very small wavelength, and is thus why we cannot see around corners. (It still can, just only a bit.)

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