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Light Propagates as
a Wave
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Wave Fronts and Light
Rays
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Light rays chart out the path that some spot on the wave front takes over time. Unless the rays bump into something, they are always straight lines. |
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Interference of Light
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Because light travels as a wave, when two waves meet, and the trough of a wave is superimposed on the crest of another, they cancel each other. When the crest of one is superimposed on the crest of another they reinforce each other. So dark and bright fringes appear, this is called the interference effect. It can only happen with waves.
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Diffraction
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The nature of a wave can be clearly seen when a small break appears in a levy. From each point of the break the waves spread out in a wave front as seen in the picture. This phenomenon is called diffraction. |
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If the break is too big the diffraction effect can get wiped out as seen in the pictures to the right. |
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Dispersion
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Refraction also depends lights color or frequency. Colors with lower frequencies like red will bend less, and colors with higher frequencies will bend more. Since white light is a combination of all the colors, as it passes through a prism the colors are separated. This is called dispersion. |
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Interference
and Dispersion
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The combination of dispersion and interference effects show up as colored fringes when we look through an oil slick on the road as shown in the two pictures below.
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Rainbows
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Rainbows are caused by dispersion. Light from the sun passes through rain drops, and its component colors exit at different angles.
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