How does the speed of light change
in different mediums?
Harris Nydegger 12/1/14
• What effect does density have on the speed of light through a
medium?
• The speed of light through air is not the same as it is through
water (Gibbs, Carlip).
• Water is more dense than air.
• Density of Substances:
• The gelatin solution I created (with a ratio of 3:1 water: gelatin solution)
has the highest density
• The gel has the next highest density.
• The soap has the lowest density.
• If I shine a laser light through different mediums then the gelatin
will have the most change of angle because it is the most dense.
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A red laser pointer
Straight sided containers (I used plastic ones)
Protractor
Card Board
Pins
Gelatin
Fructis Styles Curl Shaping Spray Gel
Green works dishwashing soap
1.Fill the container with air. (will later be substituted with gelatin,
curl spray gel, and dish soap)
2.Use the cardboard and pins to create guides that won’t allow
your containers to move.
3.Point the laser pointer at a flat side of the container using your
guides.
4.The angle of the laser pointer should be at 40 degrees (or
whatever you decided).
5.Shine the laser into the center of the water.
6.Measure the angle of refraction.
7.Repeat for all mediums.
• Constants: the temperature of the elements, the angle of
incidence, and the distance between the laser pointer and the
element.
• Control: Empty container
• Independent variable: The medium
• Dependent: The angle of refraction
• At first I noticed that the greatest angle change came at the
slightest angle of entry. However, since all of the mediums
needed to enter at the same angle so as to not skew results, this
result was interesting, but an unnecessary step. I found out that
Gelatin gives the most change in angle, curling gel the second
most, and dish soap the had the least change, however it still
exhibited change. The only medium that exhibited no visible
change was air (however I expect it has a slight change when in
a vacuum).
Medium
Air
Gelatin
Curling Spray
Gel
Dish Soap
Entry Angle
40
40
40
40
Angle Throughout Density
Medium
40
Lowest
68
Highest
62
Middle
55
Lowest (other than
the control)
80
70
60
50
Enrty Angle
40
Angle through outthe
medium
Density (In Gradual units)
30
20
10
0
Air
Gelatin
Curl Shaping Dish Soap
Gel
• P: Density has a great effect on the speed of light, more dense
objects seem to change the speed of light more than less dense
objects.
• C: My hypothesis was supported because the Gelatin showed
the greatest change in angle, which means that it has the
slowest speed throughout the medium.
• This can be used in real life to create more complex locks that
would use different combinations of materials to bend light as
well as requiring a certain wavelength of light to unlock. There
are many more applications.
• Carlip, Steve and Gibbs, Philip. “Is the Speed of Light
Constant?” http://www.desy.de/. 1997. Web. 12/19/14
• Emspak, Jesse. “Speed of Light May Not Be Constant, Physicists
Say.” http://www.livescience.com/. 27 April 2013. Web.
12/19/14.