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Reflection, Refraction and Diffraction

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What happens when waves hit a surface?

How the waves behave depends on their energy and the type of material they interact with.

For example, light waves are reflected by skin, but X-rays transmitted through skin.

If electromagnetic waves are absorbed, some of their energy is transferred to the material. This usually increases the temperature of the material.

When electromagnetic (EM) waves hit a surface, they can be reflected, absorbed or transmitted.

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Investigating reflection

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Spear fishing has been used for centuries and is still practiced by subsistence communities.

What is refraction?

As the light crosses the boundary between fluid and glass, it is bent, producing a distorted image.

The straw appears to be bent in the liquid. What is causing this effect?

This known as refraction.

To accurately spear the fish,fishermen learn to aim a short distance behind the fish’s image, in order to compensate for the effect of refraction.

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Refraction in a glass block

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Understanding why light refracts

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What is diffraction?

Diffraction is a property of all waves, which can be shown by water waves in a ripple tank.

So, when radio waves travel past an obstacle or through a narrow gap, they bend or spread out due to diffraction.

Here, the waves travel along until they reach a gap. The width of the gap is similar to the wavelength of the waves.

The waves pass through the gap and spread out. This is diffraction.

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How does wavelength affect diffraction?

The amount of diffraction depends on how the wavelength compares with the size of the gap.

What happens if the wavelength is much smaller than the width of the gap?

In this case, only the edges of the wave front are diffracted.

Maximum diffraction occurs when the wavelength is similar to the gap size.

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Why can I receive radio but not TV?