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Science

An introduction to waves

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Diffraction

When waves meet a gap in a barrier, they carry on through the gap. However, the waves spread out to some extent into the area beyond the gap. This is diffraction.

The extent of the spreading depends on how the width of the gap compares to the wavelength of the waves. Significant diffraction only happens when the wavelength is of the same order of magnitude as the gap. For example:

  • a gap much larger than the wavelength causes little spreading and a sharp shadow eg light through a doorway
  • a gap similar to the wavelength causes a lot of spreading with no sharp shadow eg sound through a doorway
Diffraction through a wide gap

Diffraction through a wide gap

Diffraction through a narrow gap

Diffraction through a narrow gap

Diffraction - Higher tier

Diffraction reduces the quality of images seen in microscopes and telescopes. It can cause rings or spikes around the image of the object being viewed.

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