PHYS 305 General Physics 3
TITLE OF THE EXPERIMENT: REFLECTION AND REFRACTION OF LIGHT
Instructor: M. Azad Islam
Studies of the change in the direction of propagation of light as it encounters an interface between two media. These studies will result in understanding the laws of reflection and refraction.
Law of reflection:
Angle of incidence = angle of reflection
Law of refraction:
Sine of angle of incidence/Sine of angle of refraction = Sinq1/ Sinq2 = Constant
Equipment needed in the experiment are HeNe laser, magnetic optical bench, component holder with angles, semicircular slab and wood board to mount the laser.
The drawing below shows the experimental arrangement:
1 = Angle of incidence
2 = Angle of reflection
3 = Angle of refraction
Procedure: Use a wood board to place the Helium-Neon Laser. Assemble the magnetic optical bench. Place a semicircular glass or plastic slab on the magnetic mount of the circular plate. Use scotch tape to mount the semicircular slab. Find the midpoint of the straight line part of the slab and make sure you can read the normal line made at the midpoint. Now use the Helium-Neon Gas CW (continuous wave) Laser to produce an incident beam as shown in the drawing. When correctly done (check with instructor) you should see the three beams (incident, reflected and refracted). Record the three angles of interest in a Table of Data. Reproduce this drawing on a page of your lab book. Repeat the procedure by increasing the incident angles in steps of 15 degrees until you reach 75 degrees.
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Angle of incidence 1 |
Angle of reflection 2 |
Angle of refraction 3 |
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15 degrees |
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30 degrees |
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45 degrees |
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60 degrees |
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75 degrees |
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NOTE: The angles of incidence need not be exactly integers.
Find out if the law of reflection is true by comparing the data. Determine the sine of the angle of incidence and Sine of the angle of refraction for each angle of incident. Make a second Table for presenting the new information. Calculate the index of refraction for each set of data. Is the ratio for index of refraction a constant?
Angle of incidence Angle of refraction Comparison Sine of angle of incidence Sine of angle of refraction Ratio Comparison 15 degrees 30 degrees 45 degrees 60 degrees 75 degrees
Devise a method to observe the Total Internal Reflection of light and find the critical angle of glass or plastic.
State the value of the critical angle you found out. Compare it with the value expected from the constant you determined in the first experiment.
Write down the experiment in brief and follow the guidelines in your lab information to complete a written report. Critically comment on accuracy of your experimental determination in half page of discussion.
Updated 08/30/2000