at two locations.
What are those two locations?
You can assume that the water
surface is perpendicular to the side of the container.
4.
Write down the expressions for Snell’s law at these two locations.
Remember the
one location is the critical situation where the beam ceases to leave the water.
How
is this critical situations expressed with Snell’s Law?
Also write down a
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TOTAL INTERNAL REFLECTION – 1202Lab1Prob8
trigonometric relationship that relates angles at these two locations.
You should
have 3 relationships.
5.
One relationship should be solvable for the critical angle of the first part of the
prediction.
The other two relationships can be manipulated to solve for the angle of
the trajectory of the incident laser beam in terms of the critical angle.
P
REDICTION
First, calculate the angle at which the beam ceases to exit the surface of the water.
The
angle is measured from the normal to the surface to the trajectory of the beam.
E
XPLORATION
Warning:
Laser beams may cause permanent vision impairment or blindness.
Do NOT allow the laser beam (or its reflection) to point into anybody's eye. To
avoid stray beams in the laboratory, make sure beams from your laser
terminate on a screen at all times.
Laser beams are extremely intense compared
to light from any common light source (even compared to sunlight, as viewed
from earth).
Permanent blindness may result from prolonged exposure to any
laser beam, even those from small laser pointers.
Arrange the container and shine the laser through the container.
Adjust the trajectory
of the laser and observe where the beam ends up so that you can determine if it exits the
water surface.
As you adjust the laser trajectory, does the resultant beam move in a continuous or
gradual manner or does it abruptly change?
What would you expect?
M
EASUREMENT
Once you have a solid understanding of the limitations of your measurements proceed
to measure the angles.
A
NALYSIS
Compare your angle measurements to your predicted values.
Are they within your
uncertainty?
If not, reevaluate your uncertainty and/or take your measurements again.
What is the minimum percent error you can attain?
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