Results 1 to 3 of 3

Thread: Prisms question

  1. #1
    OptiBoard Novice
    Join Date
    Mar 2018
    Dispensing Optician

    Big Smile Prisms question

    Hi can anyone help me answer this question

    Construct a triple tangent scale for use at 2.5 metres on which you could read thepower of an unknown prism in prism dioptres, degrees of deviation and degreesof apical angle (assume a refractive index of 1.523)

  2. #2
    What's up? drk's Avatar
    Join Date
    Mar 2004
    I think the gist of it is you have to do a science project.

    Like, get a piece of cardboard and put it 2.5M from a prism sitting on a table (maybe base down).

    Shine a beam of light through it. Like a cool laser! But you'd need "collimated light" I think, so get out the optical bench.

    Measure the deviation from dead center.

    Then use math to calculate prism diopters and degrees of deviation, and then plug and chug into the formula that includes the apical angle (which I only vaguely remember).

    Good luck!

    Oh, what's a triple tangent scale? I can see how one would use trigonometry, here, but they're looking for you to devise a scale to read on the cardboard that you could maybe answer all three questions (apical angle, degrees, p.d.) for any prism you'd put in there.

  3. #3
    My Brain Hurts jpways's Avatar
    Join Date
    Oct 2008
    NW PA
    Dispensing Optician
    When I googling for a tangent scale I came across this
    Which could be used to measure prism, but I doubt that's called a triple tangent scale as it's only in 2 axes, maybe the 3rd axis is an object that measures/controls distance since you would need a way to convert the distance to 1m to properly measure prism.
    Last edited by jpways; 03-13-2018 at 01:35 PM.

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Similar Threads

  1. Prisms
    By rekha in forum Ophthalmic Optics
    Replies: 5
    Last Post: 02-11-2013, 03:20 PM
  2. Prisms prisms prisms
    By RetroRat in forum General Optics and Eyecare Discussion Forum
    Replies: 10
    Last Post: 09-17-2010, 03:35 AM
  3. Help with prisms!
    By Whitwoo in forum Ophthalmic Optics
    Replies: 7
    Last Post: 07-19-2008, 01:13 PM
  4. Help for Resultant Prisms
    By Shutterbug in forum Ophthalmic Optics
    Replies: 1
    Last Post: 10-22-2003, 11:09 AM


Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
OptiBoard is proudly sponsored by:
BC College of Optics, Younger Optics and Vision Equipment