# Phy Lab Essay

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Geometrical Optics: Snell's Law

PHY101 Lab 12
Date: July 23rd, 2012

Objective:
The purpose of this laboratory activity is to develop a set of experimental procedures that answer questions regarding Snell's Law and the index of refraction. Ultimately, the experimental procedures you develop will allow the index of refraction to be found for water and cooking oil.

1. Explain how to experimentally determine the index of refraction of two substances. 2. Develop a set of experimental procedures to find the index of refraction for water and cooking oil. 3. Calculate the index of refraction using Snell's Law. 4. Explain critical angle and total internal reflection.

Materials

Materials from Lab Kit:
Laser
4. Once the ray goes through and refracts in the oil and comes out to air from the curving side of the cell, record the point the ray comes out by drawing a dot on the paper using the pencil. 5. Record the line that the light goes from air to oil, and connect the dot with the intersection point of the vertical line and flat cell side. 6. Measure the angle Θ2andφ2.

DATA
When light passes from one medium to another, air to water for example, part of the light is reflected at the boundary and part of the light gets bent as it passes on to the new medium. The bending of this light is referred to as refraction. A sketch of this is shown below.

In this example, n1 is the index of refraction for air. The index of refraction for water is n2. According to Snell's Law:

n1 sin Θ = n2 sin φ

n(air)=1
Note: The angles are measured with respect to the normal (vertical).

Part of the scientific method is to develop laboratory procedures that test a hypothesis and answer a scientific question.

Construct an Excel spreadsheet to calculate the index of refraction for water and cooking oil. Remember that in Excel angular measurement is in radians. Pi radians = 180 degrees.

Record Data from the Experiment

| Θ1 | φ1 | Θ2 | φ2 | Angle | 41.5o | 29.9o | 41.5o | 22.5o | radian | 0.23 pi | 0.166 pi | 0.23 pi | 0.125 pi |

Calculations—Calculate the Index of Refraction

Record Data from the