Snell’s Law Lab Activity
In this activity you will find out if the angle of incidence of a ray that strikes an acrylic dish compares with:
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The angle of reflection
The angle of refraction of the acrylic dish
Pre-Lab Questions:
1. What is Snell’s Law and what is it used for?
2. Write out what each of the variables represents.
3. Re-arrange Snell’s Law to solve for n1 and n2.
Materials:
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__________ half circle
Protractor
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Graph paper
Ruler
Ray box with single slit
plate
Procedure:
1. Draw a horizontal line on graph paper. Label the line as: Normal.
2. Draw a perfectly perpendicular line to your normal. Label the intersection as O (origin).
3. Use a protractor and draw lines with angles of incidence that are 10, 20, 30, 40, 50 from the
normal.
4. Line up your half circle on the perpendicular line so it is split in half by the normal.
5. Direct a single ray from a ray box along your angled lines of incidence. Mark the line of reflection and
refraction.
6. Draw all lines in full and measure all angles of reflection and refraction.
normal
i1
r1
R1
Observations:
Air
Angle of Incidence (i)
0
10
20
30
40
50
Angle of Reflection (r)
Unknown
Angle of Refraction (R)
7. Using a scientific calculator, find the sine value of the Angles of Incidence and Angles of Refraction.
Air
Angle of Incidence (i)
0
10
20
30
40
50
sini
Unknown
Angle of Refraction (R)
sinR
8. Using the Snell`s Law calculation, find the index of refraction for your unknown substance at each angle
(6 calculations total). After this is complete, take an average of your results to find a final index of
refraction. PLEASE SHOW YOUR WORK!!!
9. Research the likely identity of the unknown substance, by comparing which substance(s) BEST match
your value for the index of refraction.
10. Compare your value, and identity to 2 other groups.
Conclusion: Answer using complete sentences.
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What was the identity of the unknown object? How did your results compare to the other 2 groups?
How could you explain any differences you may have had in your results or conclusions?
Explain the significance of the measuring the values for r.
Identify and explain and sources of error in this experiment that could alter your results.
WHAT TO SUBMIT:
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Pre-Lab Questions
Drawings
Observation tables
Calculations (Show complete work for 1 of each type of calculation)
Conclusion paragraph