# What's this optical dispersing prism called?

**URL:** <https://boards.straightdope.com/t/whats-this-optical-dispersing-prism-called/467672>\
**Category:** Factual Questions\
**Created:** [October 13, 2008, 3:43am UTC](https://boards.straightdope.com/t/whats-this-optical-dispersing-prism-called/467672 "2008-10-13T03:43:58Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![Napier](https://avatars.discourse-cdn.com/v4/letter/n/ce73a5/32.png) [@Napier](https://boards.straightdope.com/u/Napier)\
**Post date:** [October 13, 2008, 3:43am UTC](https://boards.straightdope.com/t/whats-this-optical-dispersing-prism-called/467672/1 "2008-10-13T03:43:58Z")

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There is a multiple-element prism used in optics just for dispersing light by color, while allowing the light to pass straight through (for some middle wavelength like 515 nm). It is long and of rectangular or square cross section, and has entry and exit faces at the ends. The light travels along the long axis. There are alternating wedges of glass cemented together, the wedges having similar indices of refraction but very different indices of dispersion. Since indices of dispersion don’t really vary all that much in absolute terms, this prism gives a fairly small dispersion for such a large and expensive piece of glass, but it has its uses. I know that it is used in some handheld spectroscopes, and I saw them advertised in a catalog once, and have certainly seen diagrams of them, but can’t find any of that now. I thought it was called a “Nicole prism”, but that is just one of several similar-looking polarizing prisms. Though it only has two elements, a Nicole prism does look like a short and simple version of the thing I’m talking about.

Anybody know???

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**Author:** ![Fear\_Itself](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/fear_itself/32/19637_2.png) [@Fear\_Itself](https://boards.straightdope.com/u/Fear_Itself)\
**Post date:** [October 13, 2008, 4:01am UTC](https://boards.straightdope.com/t/whats-this-optical-dispersing-prism-called/467672/2 "2008-10-13T04:01:38Z")

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A [Double Amici prism](http://ioannis.virtualcomposer2000.com/spectroscope/amici.html)?

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**Author:** ![Napier](https://avatars.discourse-cdn.com/v4/letter/n/ce73a5/32.png) [@Napier](https://boards.straightdope.com/u/Napier)\
**Post date:** [October 13, 2008, 10:29am UTC](https://boards.straightdope.com/t/whats-this-optical-dispersing-prism-called/467672/3 "2008-10-13T10:29:46Z")

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Wow, Fear, thanks - I think you’ve got it!

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**Author:** ![CalMeacham](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/calmeacham/32/35_2.png) [@CalMeacham](https://boards.straightdope.com/u/CalMeacham)\
**Post date:** [October 13, 2008, 1:19pm UTC](https://boards.straightdope.com/t/whats-this-optical-dispersing-prism-called/467672/4 "2008-10-13T13:19:59Z")

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Actually, it’s more commonly called a _Direct Vision Prism_. That’s what we generally called them, and it’s how it’s entered in **The Penguin Dictionary of Physics**. The name Double Amici Prism can be confusing a.) because Amici prisms are often used to re-direct light by 90 degrees, often interchanging right and left as well (as in Smith’s **Modermn optical Engineering** and b.) Some Direct-Vision Spectroscopes use more than three elements. The one sold by Edmund Optical has five:

[http://www.edmundoptics.com/onlinecatalog/displayproduct.cfm?productID=1901](http://www.edmundoptics.com/onlinecatalog/displayproduct.cfm?productID=1901)

Here’s one that covers all bases – an **Amici Direct Vision Prism** :

> **[Simulation and skills training for Medical Education - 3B Scientific](https://www.3bscientific.com/us/index.html)**
>
> Medical Simulation, Medical Education, Medical Simulators, Human anatomy models and charts, Physics equipment and Biology supplies, Science Education, Physiotherapy and Acupuncture supplies

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**Author:** ![Napier](https://avatars.discourse-cdn.com/v4/letter/n/ce73a5/32.png) [@Napier](https://boards.straightdope.com/u/Napier)\
**Post date:** [October 13, 2008, 4:16pm UTC](https://boards.straightdope.com/t/whats-this-optical-dispersing-prism-called/467672/5 "2008-10-13T16:16:22Z")

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I’ve had the Edmund device for years. It’s very handy.

Can’t find my Penguin dictionary, and neither term is in the index of my Handbook of Optics. The spectroscopy chapter is only about the data, not the equipment.

Thanks!