Chapter 33

1. Chapter 33 The Nature and Propagation of Light (cont.)

2. Dispersion: The index of refraction depends on the wavelength of the light. See Figure 33.18 (right). • Figure 33.19 (below) shows dispersion by a prism. Dispersion

3. The formation of a rainbow is due to the combined effects of dispersion, refraction, and reflection. (See Figure 33.20 below and on the next slide.) Rainbows—I

4. Rainbows—II

5. 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

6. 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

7. An electromagnetic wave is linearly polarized if the electric field always points along one direction. • Figure 33.23 at the right shows a Polaroid polarizing filter. Polarization

8. Figure 33.25 below shows a polarizer and an analyzer. • Malus’s law: I = Imaxcos2. • Read Problem-Solving Strategy 33.2. • Follow Example 33.5. Malus’s law

9. Q33.5 Three polarizing filters are stacked with the polarizing axes of the second and third filters oriented at 45° and 90°, respectively, relative to the polarizing axis of the first filter. Unpolarized light of intensity I0 is incident on the first filter. The intensity of light emerging from the third filter is

10. A33.5 Three polarizing filters are stacked with the polarizing axes of the second and third filters oriented at 45° and 90°, respectively, relative to the polarizing axis of the first filter. Unpolarized light of intensity I0 is incident on the first filter. The intensity of light emerging from the third filter is

11. When light is reflected at the polarizing angle p, the reflected light is linearly polarized. See Figure 33.27 below. Polarization by reflection

12. Brewster’s law: tan p = nb/na. • At the polarizing angle, the reflected and refracted rays are perpendicular to each other. See Figure 33.28 at the right. Brewster’s law

13. Q33.6 Natural light is incident on the surface of a liquid. The reflected light will be completely polarized if the incident angle qa is A. greater than the polarizing angle. B. greater than or equal to the polarizing angle. C. equal to the polarizing angle. D. less than or equal to the polarizing angle. E. less than the polarizing angle.

14. A33.6 Natural light is incident on the surface of a liquid. The reflected light will be completely polarized if the incident angle qa is A. greater than the polarizing angle. B. greater than or equal to the polarizing angle. C. equal to the polarizing angle. D. less than or equal to the polarizing angle. E. less than the polarizing angle.

15. Circular polarization results from the superposition of two perpendicularly polarized electromagnetic waves having equal amplitude but a quarter-cycle phase difference. The result is that the electric field vector has constant amplitude but rotates about the direction of propagation. (Figure 33.30 below.) Circular polarization

16. Scattering occurs when light has been absorbed by molecules and reradiated. • Figure 33.32 below shows the effect of scattering for two observers. Scattering of light

17. Clouds are white because they scatter all wavelengths efficiently. See Figure 33.33 below. Why are clouds white?