Chapter 33

17
© 2012 Pearson Education, Inc. { { Chapter 33 Chapter 33 The Nature and Propagation of Light The Nature and Propagation of Light (cont.) (cont.)

description

Chapter 33. The Nature and Propagation of Light (cont.). 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. - PowerPoint PPT Presentation

Transcript of Chapter 33

Page 1: Chapter 33

© 2012 Pearson Education, Inc.

{{Chapter 33Chapter 33

The Nature and Propagation of Light (cont.)The Nature and Propagation of Light (cont.)

Page 2: Chapter 33

© 2012 Pearson Education, Inc.

DispersionDispersion• DispersionDispersion: The index of : The index of

refraction depends on the refraction depends on the wavelength of the light. See wavelength of the light. See Figure 33.18 (right).Figure 33.18 (right).

• Figure 33.19 (below) shows Figure 33.19 (below) shows dispersion by a prism.dispersion by a prism.

Page 3: Chapter 33

© 2012 Pearson Education, Inc.

Rainbows—IRainbows—I• The formation of a rainbow is due to the combined The formation of a rainbow is due to the combined

effects of dispersion, refraction, and reflection. effects of dispersion, refraction, and reflection. (See Figure 33.20 below and on the next slide.) (See Figure 33.20 below and on the next slide.)

Page 4: Chapter 33

© 2012 Pearson Education, Inc.

Rainbows—IIRainbows—II

Page 5: Chapter 33

© 2012 Pearson Education, Inc.

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 crit.

In order for total internal reflection to occur, what must be true about na, nb, and the incident angle a?

A. na > nb and a > crit

B. na > nb and a < crit

C. na < nb and a > crit

D. na < nb and a < crit

Page 6: Chapter 33

© 2012 Pearson Education, Inc.

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 crit.

In order for total internal reflection to occur, what must be true about na, nb, and the incident angle a?

A33.4

A. na > nb and a > crit

B. na > nb and a < crit

C. na < nb and a > crit

D. na < nb and a < crit

Page 7: Chapter 33

© 2012 Pearson Education, Inc.

PolarizationPolarization

• An electromagnetic An electromagnetic wave is wave is linearly linearly polarizedpolarized if the electric if the electric field always points field always points along one direction.along one direction.

• Figure 33.23 at the Figure 33.23 at the right shows a Polaroid right shows a Polaroid polarizing filterpolarizing filter..

Page 8: Chapter 33

© 2012 Pearson Education, Inc.

Malus’s law Malus’s law

• Figure 33.25 below shows a polarizer and an Figure 33.25 below shows a polarizer and an analyzer.analyzer.

• Malus’s lawMalus’s law: : I = II = Imaxmaxcoscos22..• Read Problem-Solving Strategy 33.2.Read Problem-Solving Strategy 33.2.• Follow Example 33.5.Follow Example 33.5.

Page 9: Chapter 33

© 2012 Pearson Education, Inc.

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

Q33.5

0

0

0

0

0

A. .

B. / 2.

C. / 2.

D. / 4.

E. /8.

I

I

I

I

I

Page 10: Chapter 33

© 2012 Pearson Education, Inc.

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

0

0

0

0

0

A. .

B. / 2.

C. / 2.

D. / 4.

E. /8.

I

I

I

I

I

Page 11: Chapter 33

© 2012 Pearson Education, Inc.

Polarization by reflectionPolarization by reflection

• When light is reflected at the When light is reflected at the polarizing angle polarizing angle pp, the reflected , the reflected light is linearly polarized. See Figure 33.27 below. light is linearly polarized. See Figure 33.27 below.

Page 12: Chapter 33

© 2012 Pearson Education, Inc.

Brewster’s lawBrewster’s law• Brewster’s lawBrewster’s law: :

tan tan pp = = nnbb//nnaa. . • At the polarizing At the polarizing

angle, the reflected angle, the reflected and refracted rays and refracted rays are perpendicular are perpendicular to each other. See to each other. See Figure 33.28 at the Figure 33.28 at the right.right.

Page 13: Chapter 33

© 2012 Pearson Education, Inc.

Natural light is incident on the surface of a liquid.

The reflected light will be completely polarized if the incident angle a is

Q33.6

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.

Page 14: Chapter 33

© 2012 Pearson Education, Inc.

Natural light is incident on the surface of a liquid.

The reflected light will be completely polarized if the incident angle a is

A33.6

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.

Page 15: Chapter 33

© 2012 Pearson Education, Inc.

Circular polarizationCircular polarization• Circular polarizationCircular polarization results from the superposition of results from the superposition of

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

Page 16: Chapter 33

© 2012 Pearson Education, Inc.

Scattering of lightScattering of light

• ScatteringScattering occurs when light has been occurs when light has been absorbed by molecules and reradiated.absorbed by molecules and reradiated.

• Figure 33.32 below shows the effect of Figure 33.32 below shows the effect of scattering for two observers.scattering for two observers.

Page 17: Chapter 33

© 2012 Pearson Education, Inc.

Why are clouds white?Why are clouds white?• Clouds are white because they scatter all Clouds are white because they scatter all

wavelengths efficiently. See Figure 33.33 below.wavelengths efficiently. See Figure 33.33 below.