Code Number: 6A42.44

Demo Title: Refraction - Number of Objects

Condition: Excellent

Principle: Refraction of Light Waves

Area of Study: Optics

Equipment:

Water tank, fish or orange golf ball.

Procedure:

Place the tank so that you can view it into one of the corners. Put the golf ball or other objects in the tank so that they are in the middle of the tank and behind the viewing corner. Multiple images of the single object will be seen.

References:

Seungjin Kim, Jiwon Lee, "How Many Fish Are in the Tank? A Demonstration of Refraction and Total Internal Reflection of Light", TPT, Vol. 63, #6, Sept. 2025, p. 432.
P.J. Ouseph, "How Many Fish Are in the Tank?" TPT, Vol. 25, # 7, Oct. 1987, p. 440.
Robert Ehrlich, "10.9, Seeing Double in a Square Container", Why Toast Lands Jelly-Side Down, p. 159.

Disclaimer

These demonstrations are provided only for illustrative use by persons affiliated with The University of Iowa and only under the direction of a trained instructor or physicist. The University of Iowa is not responsible for demonstrations performed by those using their own equipment or who choose to use this reference material for their own purpose. The demonstrations included here are within the public domain and can be found in materials contained in libraries, bookstores, and through electronic sources. Performing all or any portion of any of these demonstrations, with or without revisions not depicted here entails inherent risks. These risks include, without limitation, bodily injury (and possibly death), including risks to health that may be temporary or permanent and that may exacerbate a pre-existing medical condition; and property loss or damage. Anyone performing any part of these demonstrations, even with revisions, knowingly and voluntarily assumes all risks associated with them.

Instructional Resources and Lecture Demonstrations

6A42.44 - Refraction - Number of Objects

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