Physics: Systems and Applications
 

Student Exercise Manual Features
Student Edition

Teacher's Manual

Student Exercise Manual

Links
  • 340 pages, 3-hole punched, shrink-wrapped, consumable
  • Follows the Student Edition
  • Includes the Labs, Questions and Problems with workspace provided
  • Included on the Teacher Component Disc as Word files

Below is an excerpt from page 347 of Unit L in the Student Exercise Manual.
Lab L-4: Colors in Thin Films and Plates

Purpose
  • To observe the colored patterns which form when light strikes a thin film or passes through a thin air space between transparent plates.
  • To interpret these results using both particle and wave models of light.

Materials
  • soap solution (70 mL dish detergent, 185 mL glycerine, 225 mL water)
  • small dish
  • metal ring (a canning jar lid works very well for this)
  • several clean microscope slides or clean, flat pieces of plate glass

Draw your apparatus:

 

 


Procedure

Part I
  1. Pour the soap solution into the dish and place the metal ring in the solution. Gently withdraw the ring from the solution, making sure that a thin film forms. Allow the ring to drain for a moment.
  2. Tilt the ring and observe the reflected light.
  3. Make simple sketches of what you observe. Be sure to note the colors and the order in which they appear.

Part II

  1. Place two very clean microscope slides in contact (see diagram). Tilt the slides and observe the reflected light from the thin air space between the slides. Make sure to sketch the results and note the color pattern produced.
  2. Place the slides on a table and adjust your line of sight so that you can again see the color pattern. With a pencil or pen tip, slowly press down on the top slide. Observe and record the patterns and changes that happen to the colors.

Analysis
Explain your observations by thinking of light as particles and then waves. Discuss this in class and compare observations. The following questions will aid you in your analysis:
  1. In what order did the colors appear for both the soap film and the slides?
  2. Can you explain this phenomenon as the result of refraction? Why or why not?
  3. Did you notice any dark areas on the soap film? They do occur. How might they be caused?


Questions (p.350)
  1. Why are the fractions 1/2, 3/2, and 5/2 appropriate subscripts for the nodal line?
  2. With respect to the path difference, what is the distinguishing feature between nodal and antinodal lines?
  3. A little water beetle swims from left to right across the water disturbance represented by the figure on page 351 of your textbook. Where will the water appear calm?


Problems (p.352)
The subscripts used in these problems relate to the path difference in wavelengths just like that in the examples above. Take 200 mm/s to be the wave speed for all problems.

  1. A point on line A2 is 100 mm from SA and 120 mm from SB. What is the wavelength?
  2. A point on N5/2 is 210 mm from SA and 180 mm from SB. Determine the wavelength.
  3. A point on A5 is 200 mm from SA and 240 mm from SB. Determine the wavelength and frequency of the disturbance.
  4. What wavelength will cause N5/2 to occur at a point 150 mm from SB and 210 mm from SA?
  5. What frequency will cause A2 to pass through a point 120 mm from SA and 60 mm from SB?
  6. What distance from SB might a point be on A3 that is 220 mm from SA when the frequency is 5 Hz? There are two answers.
  7. What distance from SB might a point be on N3/2 that is 200 mm from SA when the frequency is 8 Hz? There are two answers.