Science - Physics - Optics - 3 Refraction
(P1064600)
3.4 Refraction at the boundary between two
liquids
Experiment by: linear motion wiht timer
Printed: Jan 10, 2011 11:59:25 AM
interTESS (Version 10.03 B132, Export 1678)
Task
Task
Why is light refracted at the boundary between two liquids?
1. Measure the angle of refraction as a function of the angle of incidence at the boundary between
air and water or air and glycerine.
2. Measure the angle of refraction as a function of the angle of incidence at the boundary between
water and glycerine.
Use the space below for your own notes.
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Logged in as a teacher you will find a button below for additional information.
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Material
Material
Material from "TESS-Optics OE 1" (Order No. 13276.88)
Position No.
Material
Order No. Quantity
1
Optical disk
09811.00
1
2
Cuvette, double semicircular, r = 30 mm
09810.06
1
3
Light box, halogen 12 V / 20 W
09801.00
1
4
... with single-slit/double-slit aperture
1
Additional Material
5
Power Supply, 0...12 V DC / 6 V, 12 V AC
13505.93
1
Glycerol, 99%, 250 ml
30084.25
20 ml
(36011.01)
2
Beaker, approx. 100 ml
Material required for the experiment
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Setup
Setup
Attention
Pay particular attention that in all parts of the experiment the narrow light beam coming from the
light box always travels constantly in the direction of the centre of the optical disk and that the
cuvette's position is not changed on moving the light box.
• Lay the optical disk in front of you on the table, position the cuvette precisely within the
markings at the line intersection.
• The partition inside the cuvette must be at a right angle to the optical axis, i.e. on the
perpendicular line.
• Insert the single-slit aperture in the light box on the lens end and position the light box at
a distance of about 1 cm away from the optical disk (Fig. 1).
Fig. 1
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Action
Action
1. Passage of light from air into liquid
• Fill the half of the cuvette facing away from the light box carefully with approximately 20 ml
of water (Fig. 2).
Fig. 2
• Connect the light box to the power supply (12 V AC) and switch it on (Fig. 3).
Fig. 3
• Move the light box until the narrow light beam travels precisely along the optical axis (Fig. 4).
• If the light box and the cuvette are adjusted properly, the narrow light beam will continue
along the optical axis after passing through the water.
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Fig. 4
• Move the light box until the light falls on the cuvette with an angle of incidence α of 30° (in
relation to the perpendicular incidence) (Fig. 5).
• Read the corresponding angle of refraction and record the value in Table 1 on the Results
page.
• Repeat this procedure for angles of incidence α of 45° and 60° and write down the
corresponding values for the angle of refraction β.
• Pour the water out of the cuvette, dry it and fill it with approximately 20 ml of glycerine.
• Repeat the experiment with glycerine and record all measured values.
Fig. 5
2. The passing of light from water to glycerine
• One half of the cuvette is filled with glycerine. Carefully fill the other half with approximately
20 ml of water. The liquids must not be mixed!
• Now position the cuvette as in the first part of the experiment.
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Fig. 6
Fig. 7
• Let the light shine on the cuvette with the angles of incidence α of 30°, 45° and 60° and note
the corresponding angles of refraction β in Table 2 on the Results page.
• Switch off the power supply.
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Results
Results
1. Passage of light from air into liquid
Table 1
Angle of incidence α in °
Air
Angle of refraction β in °
Water
Glycerine
30
nnnnnnnnnn nnnnnnnnnn
45
nnnnnnnnnn nnnnnnnnnn
60
nnnnnnnnnn nnnnnnnnnn
2. Passage of light from water into glycerine
Table 2
Angle of incidence α in °
Angle of refraction β in °
Water
Glycerine
30
nnnnnnnnnn
45
nnnnnnnnnn
60
nnnnnnnnnn
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Evaluation
Evaluation
Question 1
Compare the angles of incidence α with the corresponding angles of refraction β from Table 1.
At which boundary was the light more strongly refracted?
Question 2
Arrange the three materials water, air and glycerine according to their optical density.
Question 3
Compare the angle of incidence α with the corresponding angle of refraction β from Table 2. How
do the narrow beams of light behave when they hit the boundary between water and glycerine at
an angle?
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Question 4
Try to give an explanation for the observed behaviour of the narrow light beams at the boundary
between water and glycerine.
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Supplementary Problems
Supplementary Problem
Question 1
Calculate the refractive indices of water and glycerine from the measured values in Table 1.
• Draw a circle like the one shown in Fig. 8 with a radius of 5 cm. Draw in all angles α and ß
from Table 1. Measure the corresponding half cords a and b.
• Record all these values in Table 3.
• Calculate the corresponding quotients n = a/b and the mean nW and nGl (refractive indices).
Fig. 8
Table 3
Air
α in °
Water
a in cm
β in °
b in cm
Glycerine
nw
β in °
b in cm
nGl
30
nnnnnnnnnn nnnnnnnnnn nnnnnnnnnn nnnnnnnnnn nnnnnnnnnn nnnnnnnnnn nnnnnnnnnn
45
nnnnnnnnnn nnnnnnnnnn nnnnnnnnnn nnnnnnnnnn nnnnnnnnnn nnnnnnnnnn nnnnnnnnnn
60
nnnnnnnnnn nnnnnnnnnn nnnnnnnnnn nnnnnnnnnn nnnnnnnnnn nnnnnnnnnn nnnnnnnnnn
mean
nW = nnnnnnnnnn
nGl = nnnnnnnnnn
Question 2
In the same way, calculate the relative refractive index nW/Gl for the water/glycerine boundary
(Table 4).
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Table 4
Water
Glycerine
α in °
a in cm
β in °
b in cm
nW/Gl
30
nnnnnnnnnn
nnnnnnnnnn
nnnnnnnnnn
nnnnnnnnnn
45
nnnnnnnnnn
nnnnnnnnnn
nnnnnnnnnn
nnnnnnnnnn
60
nnnnnnnnnn
nnnnnnnnnn
nnnnnnnnnn
nnnnnnnnnn
Average
nW/Gl = nnnnnnnnnn
Question 3
Try to find a relationship between the refractive indices nW and nGI and the relative refractive index
nW/GI.
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