REFLECTION and REFRACTION
of LIGHT
PROCEDURE
Set up the apparatus as shown in Fig. 14-2, and turn on the light source. The room should be dark enough that the light rays on the Ray Table are visible. Carry out the following procedures.
Figure 14-2: Apparatus for Light Ray Observation
Straight Line Propagation of Light:
3. Rotate the Slit Plate slowly on the component holder until the slits are horizontal. Observe the slit images on the Viewing Screen and answer Questions 3 through 5 on the Worksheet.
Figure 14-3: Ray Tracing
5. Remove the paper. Use the pencil and straight edge to extend each of the rays back to the source. Trace them back to their common point of intersection. You may need to tape on an additional sheet of paper. Label the filament location and the center of the Ray Table on your diagram.
6. Use the scale on the Optics Bench to measure the distance between the filament and the center of the Ray Table directly. Record the distance in cell F49.
Figure 14-4: Law of Reflection Set Up
8. 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. 14-5.
The plane that contains the incident ray and the normal to the mirror is called the plane of incidence. In this experiment, the plane of incidence is the top surface of the Ray Table.
9. 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 cells D55:D64 of the Data Table on the Worksheet.
Answer Question 6 on the Worksheet.
Figure 14-6: Determination of Image Location
11. 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 7 on the Worksheet.
12. With a pencil, mark two points along one edge of each of the incident and reflected rays. Label the points r1, r2, etc., so that you know which points belong to which ray.
13. Remove the paper and reconstruct the rays as shown in Fig. 14-6, 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 d1 and the apparent position of its reflected image d2.
14. Change the position of the mirror and repeat the measurements for a different orientation of the mirror.
Figure 14-7: Law of Refraction Set Up
16. 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 θi to: 0°, 10°, 20°, 30°, 40°, 50°, 60°, 70°, 80°, and 90°. For each angle of incidence θi, measure and record the angle of refraction θr in cells D87:D96 on the Worksheet.
Figure 14-8: Ray Table Set Up for Refraction
17. Obtain a print out of your Worksheet and use it to develop your lab report.