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Physics- how does material of the lens or use of a colour filter affect focal length? Watch

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    Hi,
    I would really appreciate some help on explaining how the material of the lens used affects the focal length and how the use of a colour filter affects focal length.

    Any help would be very appreciated!
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    If its curved then depending on whether its concave or convex. A concave lens will always make a diminished virtual image. I dont think filters would have any effect as they simply absorb coloured light allowing only one colour to be reflected

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    (Original post by wegeton)
    Hi,
    I would really appreciate some help on explaining how the material of the lens used affects the focal length and how the use of a colour filter affects focal length.

    Any help would be very appreciated!
    Different materials have different refractive index.
    The refractive index of the material will affect the focal length.
    Other factors affecting the focal length will be the curvature of the surface.
    The formula is here
    http://en.wikipedia.org/wiki/Lens_(o...r.27s_equation

    Light of different wavelengths is refracted different amounts.
    Shown here
    http://mistupid.com/science/prism.htm
    eg blue light is refracted more than red in glass. Another way of putting it is to say that the refractive index depends on wavelength.
    In which case the focal length will depend on wavelength and therefore on the colour of the light used.
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    Thanks, this has really helped!
 
 
 
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