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Simplest lens set up to reveal optical spectra of an object

  1. Jun 5, 2015 #1
    I have done basic experiments where a laser is shot thru a grating and a lens is inserted at the diffraction pattern to put the spectra back together and form an image of the grating. apart from this being the single most mind blowing experiment ever to witness I have some questions about the lens set up's.

    the experiments I did were standard undergrad (I think) done on a optical bench with converging lenses.

    the set up involved a bunch of extra lenses in front of the laser and at the image end. I can not figure what all these extra lenses are for apart from maybe bringing the image in to a convenient distance that whoever write the experiment figured out in advance.

    I am not interested in what these lenses do but am interested in the simplest set up with hopefully 2 lenses and a grating where I can get an image of the grating or an image of the spectra by just adding/removing one lens to switch between the two desired images all at a practical distance to the final image plane.

    anyone got any references/links/posts to a simple lab set up without all the extra who knows what for lenses added.

    cheers any info
  2. jcsd
  3. Jun 5, 2015 #2


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    Why did you not ask someone what all those lenses are for?

    I would not be surprised if the setup contained a beam expander/collimator. A laser light from most sources is a thin, pencil beam, and to make it go through a wide coverage of a grating, you have to expand it.

    The simplest experiment is still with just ONE convex lens if the laser spot size is big enough. That is all you need, in principle.

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