lab - refraction of light ib1 by stariya


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                                                                                                                                     IB 11

              Name: __________________________                                                        Row# ______

                                             LAB: Refraction of Light
              Research Problem: Determine the index of refraction for a substance by examining the
              paths of light rays passing through the substance.

              Materials: cardboard, 4 pins, protractor, paper, pencil, glass/plastic plate

              SAFETY: Do not perform acupuncture on yourself or your lab partner.


              1. Put the blank paper on the cardboard and place the glass plate on top of it. Outline
                 the shape of the glass plate on the paper. Remove the glass plate.

              2. Near the upper left-hand corner of the glass plate’s outline, draw a point (P) and draw
                 a normal line to the glass block at this point. Point P will be the point where all the
                 rays of light will enter the glass plate.

              3. Draw an incident ray to point P                  pins
                 at an angle of 300 with respect
                 to the normal. Stick two pins in
                 the paper on the line and put the
                 glass plate back. (See diagram.)

              4. Crouching down and looking through the thin edge of the glass plate, move your head
                 from side to side until you see the bases of the pins line up. This is your line of sight.

              5. Stick two more pins in the paper on the side of the glass plate where your eye is.
                 These two pins should be on your line of sight so that you now have the bases of all
                 four pins lined up (two on each side of the glass plate.)

              6. Remove the plate and the pins. Draw the line of sight that will connect all four pins.
                 (Hint: It shouldn’t be a straight line.)

              7. Measure and record the angle of refraction for the light ray as it entered the glass plate.

              8. Repeat steps 3 through 7 for several angles of incidence. Make sure all incident rays
                 pass through point P.
Data Collection: Measure and label the angles of incidence and refraction as the light
enters the glass block for every trial. Clearly indicate them on your diagram. Organize
your data clearly in a data table. Be sure to use appropriate labels, units and
uncertainties. Also, include in your data table the values of the sine of each angle for use
in the graph below. Be sure to attach your diagram and data table to this lab.

Data Processing: (On separate paper.) Plot a graph of the sine of the angle of incidence          [20]
(sin θ1) versus the sine of the angle of refraction (sin θ2). Write a specific equation for
your graph. Determine the index of refraction from your graph. Show how you
determined this value.

Conclusion: (On separate paper) Write a well-written paragraph summarizing the                    [5]
purpose and results of this lab. Be sure to compare your results to a literature value.

Questions: (Answer below.)                                                                        [15]

1. As the ray of light entered the glass, how did it bend with respect to the normal?

2. As the ray of light exited the glass, how did it bend with respect to the normal?

3. As the ray of light entered the glass, its
   a) speed (increases/decreases/remains the same)?

   b) frequency (increases/decreases/remains the same)?

   c) phase (changes/remains the same)?

   d) period (increases/decreases/remains the same)?

   e) wavelength (increases/decreases/remains the same)?

4. Calculate the speed of light in your glass block using your experimentally derived
   value for the index of refraction.

5. Taking an average value of 5.09 x 1014 Hz for the frequency of light, determine the
   wavelength of this light in your glass block.


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