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Science

Why do scientists think that light and sound are waves?

Light travels as transverse waves and can travel through a vacuum. Sound travels as longitudinal waves and needs to travel through a solid, liquid or gas: it cannot travel through a vacuum.

Light and sound can be reflected and refracted, just like water waves. Light and sound can also be diffracted, just like water waves, but diffraction in light is less obvious than in sound.

Light and sound compared

Light and sound both travel as waves, but they are not identical. The table summarises the similarities and differences between them.

Table comparing light and sound waves

PropertyLightSound

Type of wave

Transversetransverse waves: Waves in which the vibrations happen at right-angles to the direction of travel. Light travels as transverse waves.Longitudinallongitudinal waves: Waves in which the vibrations happen in the same direction as the direction of travel. Sound waves are longitudinal waves.

Can they travel through a vacuumvacuum: A volume that contains no matter - space is almost a vacuum.?

YesNo. Sound waves can only pass through a solid, liquid or gas

Can they be reflectedreflection: There is a reflection when waves bounce off a surface.?

YesYes

Can they be refractedrefraction: There is refraction when waves change direction as they move from one transparent substance to another.?

YesYes

Can they be diffracteddiffraction: The spreading out of waves when they pass through a gap or around an obstacle.?

YesYes

Can they interfere?

YesYes

Back to Wave model of radiation index

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