Upload
nantai
View
60
Download
0
Tags:
Embed Size (px)
DESCRIPTION
Snell's Law Refraction of Light. By: Brett Rapponotti and Corrine Yap. Purpose. To determine the relationship between the angle of incidence and the angle of refraction of a light wave traveling through a medium. The media investigated in this experiment are air to plastic and water. - PowerPoint PPT Presentation
Citation preview
Snell's LawRefraction of LightBy: Brett Rapponotti and Corrine Yap
PurposeTo determine the relationship between
the angle of incidence and the angle of refraction of a light wave traveling through a medium.
The media investigated in this experiment are air to plastic and water.
Equipment Used
circle, divided into four quadrants, with one quadrant divided into separate ten degree sectors
laser beam
medium (plastic)
other medium, plastic filled with water
Procedure 1. Begin with the solid glass semicircle and align it with the diameter of the circle,
facing the quadrant divided into 10o sectors.2. Place the laser at the “0o” position and shine it through the glass. It should follow
the diameter perpendicular to the glass. Mark the light on the opposite end of the paper circle.
3. Now place the laser at 10o. Mark the refracted light on the opposite end of the circle after it has gone through the glass medium.
4. Repeat step 3, each time adding 10o, until 90o has been reached.5. Using the protractor, measure the angles of refraction. This is best done by
connecting each point to the center of the circle using a ruler and then measuring the angles from the center.
6. Plot Angle of Refraction vs. Angle of Incidence in LoggerPro.7. Draw semichords from the marked points to the perpendicular diameter, creating
right triangles. Do the same for the original angles, and plot Semichord of Refraction vs. Semicord of Incidence.
8. Determine the relationship between the angles and the semichords and also plot Sine of Angle of Refraction vs. Sine of Angle of Incidence.
9. Repeat the experiment using the hollow plastic semicircle filled with water on a new paper circle; make the same measurements and create corresponding graphs.
Data
Graphs
What Now??The angle of incidence and angle of
refraction do not have a linear relationship, although it may seem that way. So we had to find a different relationship. We decided to draw semichords from the points on the perimeter of the circle to the radii and measure them.
More Graphs
Thoughts...How is the semichord related to the
angle, then?
radius
semichord
angle
sin(θ) = semichord/radiusSo.....
Even More Graphs!
Mathematical AnalysesSine of angle of refraction = sin(ϴR) ,
Sine of angle of incidence = sin(ϴI)
sin(ϴR) = ksin(ϴI)k = ∆sin(ϴR)/∆sin(ϴI)kglass = 0.6532 (calculated by
LoggerPro)sin(ϴR) = 0.6532sin(ϴI)Sine of angle of refraction = 0.6532*Sine of angle of incidenceHm. Now what could that possibly mean?
Index of Refractiona dimensionless number that describes
the relationship between the speed of light and the nature of the medium through which it travels.
Index of refraction --> nspeed of light --> cspeed of wave --> vn = c/v
nair = 1
nplastic = 1.495kplastic (calculated by LoggerPro) = 0.65321/0.6532 = 1.531Taking error into consideration,n = 1/kTherefore,sin(θR) = sin(θI)/n for plastic.
WATER
More on Water
Even More on Water
Mathematical AnalysisSine of angle of refraction = sin(ϴR) ,
Sine of angle of incidence = sin(ϴI)
sin(ϴR) = ksin(ϴI)k = ∆sin(ϴR)/∆sin(ϴI)kwater = 0.7621 (calculated by
LoggerPro)sin(ϴR) = 0.7621sin(ϴI)Sine of angle of refraction = 0.7621*Sine
of angle of incidence (water)
Therefore,the same conclusion can be drawn. nwater = 1.33283kwater = 0.76211/0.7621 = 1.312Taking error into consideration, nwater = 1/kwater
So, sin(θR) = sin(θI)/n for water as well.
But why 1?We can't just say, oh, let's divide one by
the constant because it works out that way! One is a significant number. Remember that
nair = 1, which is also nvacuum.The angle of incidence was measured as
the light wave was traveling through air, while the angle of refraction was measured once the light traveled through a different medium.
Therefore, nair = nmedium of incidence and nplastic or nwater = nmedium of refraction
WHOA!sin(θR)/nI = sin(θI)/nR
Rearranging,nRsin(θR) = nIsin(θI)
This is Snell's Law!