18.4 Determining Indices of Refraction
Note: You will complete a similar activity in Part Two of Assignment 11.
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Lab: Determining the Refractive Index of Various MaterialsRead "Inquiry Lab" on page 671 of the text then use the two images below for your observations. Note that the same wavelength of light is used and the lines are coloured to let you match the incident ray with the refracted ray. The semi-circular dish (light blue) is placed on a circular polar paper that acts like a 360° protractor. The polar paper has a radial line every ten degrees. You can use a real protractor to measure or you can estimate the values between the lines.
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Remember, measure your angles from the normal to the surface.
Water Refractions
Ethanol Refractions
Problem
What are the refractive indexes of water and ethanol?
Materials
- polar coordinate paper
- graphing paper
- water
- ethanol
- single-slit ray box or laser
- semicircular plastic dish
Procedure
Follow the Procedure on page 671 of your textbook. If you do not have access to a supervised laboratory, use the diagrams to fill in the table and to answer the questions that follow.
Observations
Use the Water Refractions diagram and the Ethanol Refractions diagram to gather data regarding water refractions and ethanol refractions. Record your data for water refractions and your data for ethanol refractions in a table like the following. (Note: You will need two tables.)
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θ 1 |
θ 2 |
sin θ 1 |
sin θ 2 |
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10 |
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20 |
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30 |
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40 |
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50 |
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60 |
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70 |
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Graph
Plot a graph of the sine of the angle of incidence versus sine of the angle of refraction. Plot a line for water and a line for ethanol. Calculate the slope of each line on this graph.
Calculations and Questions
Complete "Analysis" questions 3 and 7 on page 671 of your textbook.