3B Scientific Basic Optics Kit User Manual
U60050 Optics
Work sheet
Experiment 7 Refractive index for transition from air to acrylic glass
Topics covered in the experiment
• The direction of a ray of light changes when it passes from air to transparent medium.
• A ray of light that is incident at an angle on a transparent body emerges from this body at a definite angle.
• If the angle of refraction is known, the refractive index can be calculated.
• The refractive index depends on the material.
Parts required
from the Student Kit – Optics (U60050)
1 optic bench
1 optical light
1 experiment table
1 single aperture slot
1 semicircular body
1 diaphragm holder
1 lens, f = +100 mm
1 overlay mask "protractor"
Setup
f = +100 mm
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Figure 1
1) Position the optical light with its exit opening on the 25 cm mark and the lens (f = +100 mm) at the 34 cm
mark on the optic bench.
2) Position the experiment table directly behind the optic bench.
3) Connect the optical light to the plug-in power supply unit.
4) Move the lens in such a way that the light spreads out in a parallel beam over the surface of the table.
5) Place the overlay mask "protractor" on the experiment table.
6) Position the diaphragm holder on the optic bench to the immediate right of the lens.
7) To create a single ray of light place the single aperture slot in the diaphragm holder and make sure that the
ray of light falls as accurately as possible on the 0° line.
8) Place the semicircular body on the overlay screen in such a way that its longitudinal side lies exactly on the
90° line and is divided into two parts by the 0° line (please see Figure 1).
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Optics / Experiment 7 Work sheet 3B STUDENT Kit
Procedure
1) Observe the path of the ray of light.
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Figure 2
2) Now turn the experiment table in such a way that the ray of light falls along the 10° mark (angle of inci-
dence α) and falls on the 0° line on the semicircular body (please see Figure 2).
3) Read off the angle at which the ray of light emerges from the semicircular body (angle of refraction β) and
the angle at which the ray of light is reflected (angle of reflection γ), and enter these values in the table.
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4) Turn the table slowly around the center of the circle in steps of 10°, up to 70°, and in each case, note down
the angle of emergence and the angle of reflection in the table. Make sure that the ray of light falls as accurately as possible on the respective degree mark and hits the semicircular body on the 0° line.
5) Using the pocket calculator, calculate the values sin α and sin β in each case, and enter them in the table.
α
sin
6) In each case, find the quotients
and note them down in the table. Round off to the second decimal
β
sin
place.
α
sin
7) Compare the quotients
in the table.
β
sin
Measurement table:
α
Angle of incidence
α
Angle of emergence
β
Angle of reflection γ sin α sin β
sin
sin
β
10° 6.5° 10° 0.17 11 1.54
20° 12.5° 20° 0.34 22 1.54
30° 19° 30° 0.50 33 1.52
40° 25.5° 40° 0.64 43 1.49
50° 30° 50° 0.77 0.50 1.54
60° 35° 60° 0.87 57 1.53
70° 39° 70° 0.94 63 1.49
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