1. How do Solutes Affect a
Solutions Angle Of
Refraction?
By, Prajwal Keranahalli
2. Background
Snell's Law describes the physics of refraction. The
index of refraction of a liquid depends on the
density of the liquid. Dissolving sugar in water
results in a solution with density greater than
that of water alone. Since sugar water is more
dense than plain water, sugar water should
have a higher index of refraction than plain
water.
3. More Background
Density of the solutes that I am going
to use:
Baking Soda: 2.20 g/cm3
Salt: 2.16 g/cm3
Sugar: 1.5620 g/cm3
4. Hypothesis
If the solute is baking soda, then the
index of refraction of the solution will
be greater, because baking soda has
more density than salt and sugar,
and greater density results in a
greater angle of refraction.
5. Independent Variable/ Dependant
Variable/ Controls
Independent Variable: The Solute
Dependant Variable: The Index of Refraction
Control:
The Index of Refraction in water with no solute(0.4)
Controls:
The Type of Container
The Type of Water
The Type of Light
The Amount of Each Solute
6. Materials
A Laser Pointer
2, 1”×3” pieces of glass
Cardboard
Measuring Cup
100 mL of Salt, Sugar, and Baking Soda
A Graphing Calculator
Electrical Tape
Epoxy glue
Tape
400 mL of Water
Glass Cutter
12in. of String
Tape measure
Graph Paper
Tooth Picks
7. Procedures
1. Cut your 1”×3” glass piece into 3 equal parts using a glass cutter.
Complete this step with adult supervision.
2. Arrange the 3 pieces of glass to form an equilateral triangular prism. Glue
it together using epoxy glue. Allow it to set.
3. Glue the prism on top of another 1”×3” glass piece. Allow it to set.
4. Take your laser and shine it perpendicular to the wall, place the empty
prism in front of the beam (the beam should not be diverted) and record
where the beam hits the prism and wall.
5. Make 3 solutions by mixing 50 mL water with 0.25 teaspoons of Salt,
Sugar, and Baking Soda.
6. Pour one of your solutions into the prism until it is almost full.
7. Shine the laser through the prism and record where the light hits the
prism and wall.
8. Repeat steps 1-7 with the other solutions
8. To Find the Index of Refraction
1. Measure the distances of X and L (indicated on the diagram), it will
define the measure of minimum deviation which will be used to find
the index of refraction.
2. Also find the distance between segment CA
3. Use X and L to find the arctangent. Opposite/Adjacent=X/L=measure
of angle of minimum deviation=Ømd
4. Plug the angle of minimum deviation into the equation:
2.00056sin(0.5(Ømd+60))
this will give you the index of refraction.
9.
10. Measurements
Sugar Salt Baking
Soda
X 134 mm. 220.2621 164.0914
mm. mm.
L 274 mm. 272 mm. 263 mm.
Segment 312 mm. 364 mm. 310 mm.
CA
Ømd 28.57 ° 41.65° 31.96°
11. Sugar Baking Soda Salt
Water Where Laser
hit the Wall
No Solution
12. Data Table
Type of Solutions Index of Refraction
Solute in
the
Trail 1 Trail 2 Trail 3 Average
Solution
Sugar 0.6 0.6 0.5 0.56
Baking 1.8 1.9 1.8 1.83
Soda
Salt 1.1 1 1.2 1.1
13. Graph
Type of Solute V.S. the Solutions Index of Refraction
2
1.5
Solutions Index of
Refraction (AVG.)
Sugar
Baking Soda
1
Salt
Water
0.5
0
Type of Solute in the Solution
14. Conclusion
Solutions with higher density had greater index of
refraction. My hypothesis was supported through
the data. Baking soda which had the most density
had more refraction than salt and sugar. It had a
refraction of 1.83 while salt was 1.1 and sugar
was 0.56. And the refraction of all the solutes
was greater than the refraction water which was
0.4. So it is proven that an increase in density
does result in a greater index of refraction. I
already knew that substances refract light but
this experiment explained to me why this
happens and why some substances refract more
light than others. I could have improved my
experiment by constantly replacing my lasers
batteries so that I so that is could get more
consistent measurements. A good follow up
experiment would be to test how different
concentrations of solute in a solution would affect
index of refraction.
