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    Hi all,

    https://imgur.com/a/1jtaX

    I’m finding this image confusing - why is the light parallel in one and not parallel in the other?

    Thanks
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    (Original post by JacobPowell)
    Hi all,

    https://imgur.com/a/1jtaX

    I’m finding this image confusing - why is the light parallel in one and not parallel in the other?

    Thanks
    The parallel light waves are wavefronts, the lines are light rays. Essentially, a ray is perpendicular to a wavefronts. It is done like this to make the image less messy.
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    (Original post by Kushala Daora)
    The parallel light waves are wavefronts, the lines are light rays. Essentially, a ray is perpendicular to a wavefronts. It is done like this to make the image less messy.
    I don’t mean the incident wave, but the two main images, where one looks like both rays meet at P and the other the rays themselves are parallel.
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    (Original post by JacobPowell)
    I don’t mean the incident wave, but the two main images, where one looks like both rays meet at P and the other the rays themselves are parallel.
    The right side image is just the left side image but zoomed in so the rays appear parallel but they aren't.
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    It's an approximation where 'D' is very much larger than 'd'. Try drawing a couple of triangles and vary both d and D and notice how the rays, r1, r2, become more or less parallel.

    In reality they are not exactly parallel, they wouldn't meet if they were!, but it is a fair approximation in a lot of cases.
 
 
 
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