• In words, describe the relation between the incident and refracted angle for a transparent substance. 4. How is the behavior of light interacting with a plane mirror similar to and different from the way light interacts with a material like the acrylic block?
71 Task #2 - Where do you see the image? Using Refracting Lenses…Equipment: 2 Glass lenses in holders (+100, -150), Optics bench, Pasco light source with an arrow pattern, viewing screen. This activity is important, but it is also kind of tricky. You may not have seen this material in lecture, but it’s important that you experience it in lab. With optics experiments, you often need to “learn what to look for”, but you can only do this by trying it out. Everyone needs to perform and participate in the following activities. Part #2-A •Securely place a light source with an arrow pattern on the optics bench. Note its position on the provided scale. •Start with the +100 lens which has a curvature like the lens in the picture below. This is called a double-convex lens or aconverging lens. •Position the lens on the optics bench 30 cm in front of the light source's arrow pattern. The arrow pattern on the light source will serve as the "object" for this activity. •Turn on the light source and move the white screen or ½screen, back and forth on the opposite side of the lens, until you see a CLEAR image of the light source. •Identify the position of the image of the arrow pattern using the measuring tape on the optics bench. •Describe the size and orientation of the image as compared to the original object. Measure and record the object distance (between the light source and the lens) and the image distance (between the lens and the position at which you see the image). When recording data for thin lenses, be sure to use the sign conventions given at the top of page 4 and as outlined in a textbook (Walker - p. 874). Carefully sketch a ray diagram that includes the object, lens, image, and depiction of your eye. Label all relevant distances in your diagram including the focal point, F. Try to make your drawing approximately to scale. 5. According to the thin lens formula, the focal length of a lens can be determined by: 1 f 1 d 0 ± 1 d i . Estimate the focal length, f , of this lens using your data. Compare the calculated focal length to the value listed on the lens holder.
72 Part #2-B • Remove the + 100 lens and viewing screen, but keep the light source in the same position as in Part #2-A.
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