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Fooled by What We See

Looking into the Water and Snell’s Law



Co Authors:

Anthony J. Creaco
Department of Science
Borough of Manhattan Community College / City University of New York
acreaco@bmcc.cuny.edu

David A. Krauss
Department of Science
Borough of Manhattan Community College / City University of New York
dkrauss@bmcc.cuny.edu

Abstract:

Most students have witnessed the refraction of light when viewing a partially submerged object—a spoon in a glass of water appears to bend—but they have little understanding of the phenomenon. The purpose of this case study is to elucidate the underlying principles and application of Snell's law to explain such illusions without the use of equations or numerical examples. It is intended to be an introduction to the topic and a starting point for the discussion of concepts related to the reflection and refraction of light through different media based on their indices of refraction. Using the familiar setting of a swimming pool, the case study relates fundamental principles of optics to observations that most students have personally experienced to explain these effects. This case study is appropriate for introductory physics classes at early college and senior high school classes. It can also serve as the basis for an informal writing assignment in writing intensive courses.

Objectives:
  • Increase interest in light wave propagation in the area of physics.
  • Improve critical thinking skills and understanding of concepts.
  • Empirically explain why light bends when passing between two transparent/translucent materials with different indices of refraction.
  • Explain that the index of refraction of a material is based on the speed of light in the material relative to the speed of light in a vacuum.
  • Explain the difference between the reflection and refraction of light and at what point reflection supplants refraction when light travels from a medium with a high index of refraction to one with a low index of refraction.
Keywords: Snell’s Law; reflection; refraction; apparent image; apparent depth; critical angle;
Topical Area: N/A
Educational Level: High school, Undergraduate lower division
Formats: PDF
Type/Method: Directed
Language: English
Subject Headings: Science (General)   Physics  
Date Posted: 7/16/2019
Date Modified: N/A
Copyright: Copyright held by the National Center for Case Study Teaching in Science, University at Buffalo, State University of New York. Please see our usage guidelines, which outline our policy concerning permissible reproduction of this work.

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