The Physics
Factbook
An encyclopedia of scientific essays

Index of Refraction of Various Household Liquids

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Refraction is the bending of incident rays due to a reduced speed in a particular medium. The index of refraction is the ratio of the speed of light to the speed of light through a particular medium or n = c/v. The index of refraction in a vacuum is 1. There can be no index smaller than one. The index of refraction in air is 1.000277.

To determine the index of refraction we filled a semi-circular tray with vinegar. The tray was then placed on this page (pdf page 2 of 2) within the outline of the semicircle. A pin was placed at the center of the semi-circle. A second pin as then placed at the 5 degree refracted ray. Looking in from the curved side close one eye and move your head until the second pin lines up with the first pin when viewed through the liquid. Take a third pin and place it on the opposite side of the tray so that all the pins line up. Repeat this step for 10, 15, 20, 25 degrees, etc. until you are unable to align all three pins. Once you have completed all the angles possible, draw straight lines from the center of the semicircle through each of the pinholes, to the end of the page. Then with a protractor, measure the angle from the y axis on the sheet and record on the chart below. Do two trials for the following substances: Heinz Vinegar, Key Food Honey, Orange Pine-Sol, Nyquil Chloraseptic, and Earth Therapeutic Foot Wash.

Complete a graph of the sines: the sine of the angle of incidence on the x-axis and the sine of the angle of refraction on the y-axis. Make a best fit line of the graph. The sines are directly proportional, so the slope of the best fit line is the index of refraction for that particular substance. We completed two trials for each of the liquids, and then took their averages.

θ1 (°) θ2 (°) sinθ1 sinθ2
5 7 0.08716 0.12187
10 13 0.17365 0.22495
15 20 0.25882 0.34202
20 28 0.34202 0.46947
25 34 0.42262 0.55919
30 40 0.50000 0.64279
35 47 0.57358 0.73135
40 57 0.64279 0.83867
45 63 0.70711 0.89101
n = 1.305
(average of two trials)

θ1 (°) θ2 (°) sinθ1 sinθ2
5 5 0.08715 0.08716
10 14 0.17365 0.24192
15 20 0.25882 0.34202
20 30 0.34202 0.5
25 38 0.42262 0.61567
30 47 0.50000 0.73135
35 58 0.57358 0.84805
40 63 0.64279 0.89101
n = 1.49
(average of two trials)

θ1 (°) θ2 (°) sinθ1 sinθ2
5 7 0.08716 0.12187
10 12 0.17365 0.20791
15 21 0.25882 0.35837
20 28 0.34202 0.46947
25 36 0.42262 0.58779
30 43 0.50000 0.68199
35 50 0.57358 0.76604
40 60 0.64279 0.86603
45 68 0.70711 0.92718
n = 1.33
(average of two trials)

θ1 (°) θ2 (°) sinθ1 sinθ2
5 9 0.08716 0.15643
10 18 0.17365 0.30902
15 26 0.25882 0.43837
20 32 0.34202 0.52992
25 39 0.42262 0.62932
30 49 0.50000 0.75472
35 55 0.57358 0.81915
40 58 0.64279 0.84805
45 62 0.70711 0.88295
n = 1.187
(average of two trials)

θ1 (°) θ2 (°) sinθ1 sinθ2
5 8 0.08716 0.13917
10 16 0.17365 0.27564
15 22 0.25882 0.37461
20 29 0.34202 0.48481
25 35 0.42262 0.57358
30 41 0.50000 0.65606
35 53 0.57358 0.79864
40 60 0.64279 0.86603
n = 1.291
(average of two trials)

Africa Belgrave, Geeta Malieckal, Bridget Ritter -- 2005

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