Set up the apparatus as shown in Fig. 12-2, and turn on the light source. The room should be dark enough that the light rays on the Ray Table are visible.
Figure 12-2: Apparatus for Light Ray Observation
Open the Worksheet and fill in the header information. Carry out the following procedures and record the answers to the questions found at the end of each step on your Worksheet.
1. Straight Line Propagation of Light: Observe the light rays on the Ray Table. Answer Questions 1 and 2 on the Worksheet.
2. Rotate the slit plate slowly on the component holder until the slits are horizontal. As you rotate the slit plate, observe the slit images on the Viewing Screen. Answer Questions 3 through 5 on the Worksheet.
3. Locating the Bulb Filament:*nbsp; Refer to the diagram in Fig. 12-3. Place a piece of blank white paper on top of the Ray Table, and make a reference mark on the paper at the position of the center of the Ray Table. Use a pencil and a straight edge to trace the edges of several of the rays onto the paper.
Figure 12-3: Ray Tracing
4. Remove the paper and tape additional paper, as needed, so that you can extend the rays backwards. Use the pencil and straight edge to extend each of the rays back towards the source. Trace them back to their common point of intersection. Label the filament location and the center of the Ray Table on your diagram. Measure the distance in centimeters from your center reference mark and the intersection of the rays. Record this on your Worksheet as distance on the diagram in cell D42.
Now, measure on the apparatus from the center reference mark to the notch on the side of the light source that marks the location of the filament. You may use the scale on the optic bench to do this. Record this on your data sheet as distance on the apparatus in cell D44.
5. Law of Reflection Use the set up shown in Fig. 12-4, with the Slit Mask in place and the Ray Optics Mirror mounted on the Ray Table. Adjust the components so that a single ray of light is aligned with the boldface arrow labeled NORMAL on the Ray Table Degree Scale. Carefully align the reflecting surface of the mirror with the boldface line labeled COMPONENT on the Ray Table. With the mirror properly aligned, the boldface arrow on the Ray Table is normal (perpendicular) to the plane of the reflecting surface.
Figure 12-4: Law of Reflection Set Up
6. Rotate the Ray Table and observe the incident and reflected light rays. The angles of incidence and of reflection are measured with respect to the normal to the reflecting surface, as shown in Fig. 12-5. In this experiment, the plane of incidence is the top surface of the Ray Table.
Figure 12-5: Ray Table Set Up for Reflection
7. By rotating the Ray Table, set the angle of incidence to successive settings of: 0°, 10°, 20°, 30°, 40°, 50°, 60°, 70°, 80° and 90°. For each angle of incidence, record the angle of reflection in the Data Table located at cell A46.
8. Image Formation in a Plane Mirror: Use the set up as before with the slit plate alone in the holder (no Slit Mask). Adjust the slit plate and the Light Source positions for sharp, easily visible rays. As shown, place a blank white sheet of paper on top of the Ray Table, and place the Ray Optics Mirror on top of the paper. Position the mirror so that all of the light rays are reflected from its flat surface. Draw a line on the paper to mark the position of the flat surface of the mirror.
9. Look into the mirror along the line of the reflected rays so that you can see the image of the Slit Plate and, through the slits, the filament of the Light Source. Answer Question 6 on the Worksheet.
10. With a pencil, mark two points along one edge of each of the incident and reflected rays. Label the points i1 for a point on incident ray #1, r2, for a point on reflected ray #2, etc. This will allow you to keep track of which points belong to which rays.
11. Remove the paper and reconstruct the rays as shown in Fig. 12-6, using a pencil and straight edge. If you need to, tape on additional pieces of paper. Draw dotted lines to extend the incident and reflected rays. On your drawing, label the position of the filament and the apparent position of its reflected image.
Figure 12-6: Determination of Image Location
12. Measure the distances from the mirror to the image and to the filament, d1 and d2, and record the values in cells D62 and D64. These distances should be the same. Are they? See Fig. 12-6.
13. Law of Refraction: Set up the equipment as shown in Fig. 12-7, using the Slit Mask and the Cylindrical Lens on the Ray Table. Adjust the components so that a single ray of light passes directly through the center of the Ray Table Degree Scale. Align the flat surface of the Cylindrical Lens with the line labeled COMPONENT. With the lens properly aligned, the radial lines that extend from the center of the Degree Scale will all be perpendicular to the circular surface of the lens itself. The angle measurement is illustrated in Fig. 12-8.
Figure 12-7: Law of Refraction Set Up
Figure 12-8: Ray Table Set Up for Refraction
14. Without disturbing the alignment of the lens, rotate the Ray Table and observe the refracted ray for various angles of incidence. By rotating the Ray Table, set the angle of incidence to: 0°, 10°, 20°, 30°, 40°, 50°, 60°, 70°, 80°, and 90°. For each angle of incidence, measure and record the angle of refraction, and enter its value in the Data Table located at cell A74.