Method to obtain convex achromatic combination

Discussion in 'Physics & Math' started by perfectionist, Jul 2, 2006.

  1. perfectionist Registered Senior Member

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    # To obtain a convex achromatic combination with 2 lenses in contact, it is necessary to combine a convex lens of lower dispersive power with a concave lens of higher dispersive power. Is it true? If so, could anyone tell me the reason for this?
     
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  3. kevinalm Registered Senior Member

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    Basically yes. The total dispersion is a funtion of both the dispersion of the glass and the focal length of the lense. For two lenses in contact and glass of equal dispersion, the only way to get a zero total dispersion is for the lenses to have focal lengths that cancel. For example a 50 mm positive convex and a -50 mm concave, so the two don't produce an image. (infinite fl)
     
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  5. perfectionist Registered Senior Member

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