Reflected image

1. Reflected image • Draw one ray from the object that enters the eye after reflecting from the mirror. Is this one ray sufficient to tell you eye/brain where the image is located? • Draw another ray to locate and label the image point. • Do any of the rays that enter the eye actually pass through the image point?

2. Constructing the image from a plane mirror II • Images from a plane mirror show left/right reversal.

3. Reflection and refraction • Figure 33.5 illustrates both reflection and refraction at once. The storefront window both shows the passersby their reflections and allows them to see inside.

4. Q33.2 Light passes from vacuum (index of refraction n = 1) into water (n = 1.333). If the incident angle qa is in the range 0° < qa < 90°, A. the refracted angle is greater than the incident angle. B. the refracted angle is equal to the incident angle. C. the refracted angle is less than the incident angle. D. the answer depends on the specific value of qa .

5. A33.2 Light passes from vacuum (index of refraction n = 1) into water (n = 1.333). If the incident angle qa is in the range 0° < qa < 90°, A. the refracted angle is greater than the incident angle. B. the refracted angle is equal to the incident angle. C. the refracted angle is less than the incident angle. D. the answer depends on the specific value of qa .

6. Q33.3 Light passes from a medium of index of refraction na into a second medium of index of refraction nb. The angles of incidence and refraction are qa and qb respectively. If na < nb, Aqa > qb and the light speeds up as it enters the second medium. B. qa > qb and the light slows down as it enters the second medium. C. qa < qb and the light speeds up as it enters the second medium. D. qa < qb and the light slows down as it enters the second medium.

7. A33.3 Light passes from a medium of index of refraction na into a second medium of index of refraction nb. The angles of incidence and refraction are qa and qb respectively. If na < nb, Aqa > qb and the light speeds up as it enters the second medium. B. qa > qb and the light slows down as it enters the second medium. C. qa < qb and the light speeds up as it enters the second medium. D. qa < qb and the light slows down as it enters the second medium.

8. Why should the ruler appear to be bent? • The difference in index of refraction for air and water causes your eye to be deceived. Your brain follows rays back to the origin they would have had if not bent. • Consider Figure 33.9.

9. Prism • Complete rays through the two prisms shown.

10. Why should sunsets be orange and red? • The light path at sunset is much longer than at noon when the sun is directly overhead.

11. Dispersion • From the discussion of the prism seen in earlier slides, we recall that light refraction is wavelength dependent. This effect is made more pronounced if the index of refraction is higher. “Making a rainbow” is actually more than just appreciation of beauty; applied to chemical systems, the dispersion of spectral lines can be a powerful identification tool.

12. Goldfish • You are looking at a goldfish in a fish tank from the top. It appears that the fish is 30 degrees below the horizontal. Where is the fish?

13. Q33.4 Light passes from a medium of index of refraction na into a second medium of index of refraction nb. The critical angle for total internal reflection is qcrit. In order for total internal reflection to occur, what must be true about na, nb, and the incident angle qa? A. na > nb and qa > qcrit B. na > nb and qa < qcrit C. na < nb and qa > qcrit D. na < nb and qa < qcrit

14. A33.4 Light passes from a medium of index of refraction na into a second medium of index of refraction nb. The critical angle for total internal reflection is qcrit. In order for total internal reflection to occur, what must be true about na, nb, and the incident angle qa? A. na > nb and qa > qcrit B. na > nb and qa < qcrit C. na < nb and qa > qcrit D. na < nb and qa < qcrit

15. Goldfish 2 • Describe what a goldfish sees if another fish swims directly overhead and moves past the angle of total internal reflection. Where is this point of total internal reflection? • Is there a spot where you cannot see the goldfish looking down from the top of the tank? • Is there a way where you can see the goldfish, but the fish can’t see you?

16. Thin lenses I

17. Thin lenses and focal point • Continue the rays through lens and out other side. • Is the point where the rays converge the same as the focal point or different? • Place a point source at the place where the rays converged. Draw several rays heading left through the lens. Do these rays converge? Would an image form?

18. Q34.8 An object PQ is placed in front of a converging lens, forming a real image P´Q´. If you use black paint to cover the lower half of the lens, A. only the object’s upper half will be visible in the image. B. only the object’s lower half will be visible in the image. C. only the object’s left-hand half will be visible in the image. D. only the object’s right-hand half will be visible in the image. E. the entire object will be visible in the image.

19. A34.8 An object PQ is placed in front of a converging lens, forming a real image P´Q´. If you use black paint to cover the lower half of the lens, A. only the object’s upper half will be visible in the image. B. only the object’s lower half will be visible in the image. C. only the object’s left-hand half will be visible in the image. D. only the object’s right-hand half will be visible in the image. E. the entire object will be visible in the image.

20. Thin lenses and images f1 f2 • An object is placed to the left of the focal point, f1. Where is its image and is the image inverted or upright? Label s, s’. Are they positive or negative? • An object is placed between the lens and the focal point, , f1. Where is its image and is the image inverted or upright? Label s, s’. Are they positive or negative?

21. Thin lenses II • Figure 34.31 at bottom left illustrates a diverging lens scattering light rays and the position of its second (virtual) focal point. • Figure 34.32 illustrates some assorted common arrangements of lens surfaces. • Follow Example 34.8.

22. Graphical methods for lenses • Figure 34.36 applies to lenses the same ray-tracing method we used for mirrors.

23. Magnifying lens • A magnifying lens with focal length 15cm is used to magnify an ant which is 10 cm away. • Draw a ray diagram of this situation • Calculate the distance the image is away from the lens • How big does the 2 mm long ant appear?

24. The camera • A clever arrangement of optics with a method to record the inverted image on its focal plane (sometimes film, sometimes an electronicarray, it depends on your camera).

25. The eye—vision problems • When the lens of the eye allows incoming light to focus in front of or behind the plane of the retina, a person’s vision will not be sharp. • Figure 34.45 (at right) shows normal, myopic, and hyperopic eyesight.

26. Vision correction—examples • Follow Example 34.13, illustrated in Figure 34.49 in the middle of the page. • Follow Example 34.14, illustrated in Figure 34.50 at the bottom of the page.

27. The microscope • Optical elements are arranged to magnify tiny images for visual inspection. Figure 34.52 presents the elements of an optical microscope.

28. The astronomical telescope • Optical elements are arranged to magnify distant objects for visual inspection. Figure 34.53 presents the elements of an astronomical telescope.

29. The reflecting telescope • Optical elements are arranged to reflect collected light back to an eyepiece or detector. This design eliminates aberrations more likely when using lenses. It also allows for greater magnification. The reflective telescope is shown in Figure 34.54.

30. Special case—dispersion and atmospheric rainbows • As a person looks into the sky and sees a rainbow, he or she is actually “receiving light signals” from a physical spread of water droplets over many meters (or hundreds of meters) of altitude in the atmosphere. The reds come from the higher droplets and the blues from the lower (as we have seen in the wavelength dependence of light refraction).

31. Selecting one orientation of the EM wave—the Polaroid • A Polaroid filter is a polymer array that can be thought of like teeth in a comb. Hold the comb at arm’s length with the teeth pointing down. Continue the mental cartoon and imagine waves oscillating straight up and down passing without resistance. Any “side-to-side” component and they would be blocked.

32. Polarization I • Read Problem-Solving Strategy 33.2. • Follow Example 33.5. • By reflection from a surface? Read pages 1139 and 1140 and then refer to Figure 33.27 below.

33. Polarization II • Consider Figure 33.28. • Follow Example 33.6, illustrated by Figure 33.29.