Light and Reflection: Characteristics, Mirrors, and Waves

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2. Resources Chapter Presentation Visual Concepts Sample Problems Transparencies Standardized Test Prep

3. Chapter 13 Light and Reflection Table of Contents Section 1 Characteristics of Light Section 2 Flat Mirrors Section 3 Curved Mirrors Section 4 Color and Polarization

4. Section 1 Characteristics of Light Chapter 14 Objectives • Identifythe components of the electromagnetic spectrum. • Calculatethe frequency or wavelength of electromagnetic radiation. • Recognizethat light has a finite speed. • Describehow the brightness of a light source is affected by distance.

5. Section 1 Characteristics of Light Chapter 14 Electromagnetic Waves • Anelectromagnetic waveis a wave that consists of oscillating electric and magnetic fields, which radiate outward from the source at the speed of light. • Lightis a form (most common example) of electromagnetic radiation. • Theelectromagnetic spectrum includes more than visible light.

6. Section 1 Characteristics of Light Chapter 14 The Electromagnetic Spectrum

7. Section 1 Characteristics of Light Chapter 14 Electromagnetic Waves, continued • Electromagnetic waves vary depending on frequency and wavelength. • All electromagnetic waves move at the speed of light. The speed of light, c, equals c = 3.00  108 m/s • Wave Speed Equation (v = fl) c = fl speed of light = frequency  wavelength

8. Section 1 Characteristics of Light Chapter 14 Electromagnetic Waves

9. Section 1 Characteristics of Light Chapter 14 Electromagnetic Waves, continued • Waves can be approximated as rays. This approach to analyzing waves is calledHuygens’ principle. • Lines drawn tangent to the crest (or trough) of a wave are calledwave fronts. • In theray approximation, lines, calledrays, are drawn perpendicular to the wave front.

10. Section 1 Characteristics of Light Chapter 14 Electromagnetic Waves, continued • Illuminance decreases as the square of the distance from the source. • The rate at which light is emitted from a source is called theluminous fluxand is measured inlumens (lm).

11. Section 2 Flat Mirrors Chapter 13 Objectives • Distinguishbetween specular and diffuse reflection of light. • Applythe law of reflection for flat mirrors. • Describe the nature of images formed by flat mirrors.

12. Section 2 Flat Mirrors Chapter 13 Reflection of Light • Reflectionis the change in direction of an electromagnetic wave at a surface that causes it (a wave) to move away from the surface. • The texture of a surface affects how it reflects light. • Diffuse reflectionis reflection from a rough, texture surface such as paper or unpolished wood. • Specular reflectionis reflection from a smooth, shiny surface such as a mirror or a water surface.

13. Section 2 Flat Mirrors Chapter 13 Reflection of Light, continued • The angle of incidenceis the the angle between a ray that strikes a surface and the line perpendicular to that surface at the point of contact. • Theangle of reflection is the angle formed by the line perpendicular to a surface and the direction in which a reflected ray moves. • The angle of incidence = the angle of reflection

14. Section 2 Flat Mirrors Chapter 13 Angle of Incidence and Angle of Reflection

15. Section 2 Flat Mirrors Chapter 13 Flat Mirrors • Flat mirrorsform virtual images that are the same distance from the mirror’s surface as the object is. • The image formed by rays that appear to come from the image point “behind” the mirror—but never really do—is called avirtual image. • A virtual image can never be displayed on a physical surface.

16. Section 2 Flat Mirrors Chapter 13 Image Formation by a Flat Mirror

17. Section 2 Flat Mirrors Chapter 13 Comparing Real and Virtual Images

18. Section 3 Curved Mirrors Chapter 13 Objectives • Calculatedistances and focal lengths using the mirror equation for concave and convex spherical mirrors. • Drawray diagrams to find the image distance and magnification for concave and convex spherical mirrors. • Distinguishbetween real and virtual images. • Describehow parabolic mirrors differ from spherical mirrors.

19. Section 3 Curved Mirrors Chapter 13 Concave Spherical Mirrors • A concave spherical mirror is a mirror whose reflecting surface is a segment of the inside of a sphere. • Concave mirrors can be used to form real images. • Areal imageis an image formed when rays of light actually pass through a point on the image. Real images can be projected onto a screen.

20. Section 3 Curved Mirrors Chapter 13 Image Formation by a Concave Spherical Mirror

21. Section 3 Curved Mirrors Chapter 13 Concave Spherical Mirrors, continued • TheMirror Equation relates object distance (p), image distance (q), and focal length (f) of a spherical mirror.

22. Section 3 Curved Mirrors Chapter 13 Concave Spherical Mirrors, continued • TheEquation for Magnification relates image height or distance to object height or distance, respectively.

23. Section 3 Curved Mirrors Chapter 13 Rules for Drawing Reference Rays for Mirrors

24. Section 3 Curved Mirrors Chapter 13 Concave Spherical Mirrors, continued • Ray diagrams can be used for checking values calculated from the mirror and magnification equations for concave spherical mirrors. • Concave mirrors can produce both real and virtual images.

25. Section 3 Curved Mirrors Chapter 13 Ray Tracing for a Concave Spherical Mirror

26. Section 3 Curved Mirrors Chapter 13 Sample Problem Imaging with Concave Mirrors A concave spherical mirror has a focal length of 10.0 cm. Locate the image of a pencil that is placed upright 30.0 cm from the mirror. Find the magnification of the image. Draw a ray diagram to confirm your answer.

27. Section 3 Curved Mirrors Chapter 13 Sample Problem, continued Imaging with Concave Mirrors • Determine the sign and magnitude of the focal length and object size. f = +10.0 cm p = +30.0 cm The mirror is concave, so f is positive. The object is in front of the mirror, so p is positive.

28. Section 3 Curved Mirrors Chapter 13 Sample Problem, continued Imaging with Concave Mirrors 2. Draw a ray diagram using the rules for drawing reference rays.

29. Section 3 Curved Mirrors Chapter 13 Sample Problem, continued Imaging with Concave Mirrors 3. Use the mirror equation to relate the object and image distances to the focal length. 4. Use the magnification equation in terms of object and image distances.

30. Section 3 Curved Mirrors Chapter 13 Sample Problem, continued 5. Rearrange the equation to isolate the image distance, and calculate. Subtract the reciprocal of the object distance from the reciprocal of the focal length to obtain an expression for the unknown image distance.

31. Section 3 Curved Mirrors Chapter 13 Sample Problem, continued Substitute the values for f and p into the mirror equation and the magnification equation to find the image distance and magnification.

32. Section 3 Curved Mirrors Chapter 13 Sample Problem, continued • Evaluate your answer in terms of the image location and size. The image appears between the focal point (10.0 cm) and the center of curvature (20.0 cm), as confirmed by the ray diagram. The image is smaller than the object and inverted (–1 < M < 0), as is also confirmed by the ray diagram. The image is therefore real.

33. Section 3 Curved Mirrors Chapter 13 Convex Spherical Mirrors • Aconvex spherical mirroris a mirror whose reflecting surface is outward-curved segment of a sphere. • Light rays diverge upon reflection from a convex mirror, forming a virtual image that is always smaller than the object.

34. Section 3 Curved Mirrors Chapter 13 Image Formation by a Convex Spherical Mirror

35. Section 3 Curved Mirrors Chapter 13 Sample Problem Convex Mirrors An upright pencil is placed in front of a convex spherical mirror with a focal length of 8.00 cm. An erect image 2.50 cm tall is formed 4.44 cm behind the mirror. Find the position of the object, the magnification of the image, and the height of the pencil.

36. Section 3 Curved Mirrors Chapter 13 Sample Problem, continued Convex Mirrors Given: Because the mirror is convex, the focal length is negative. The image is behind the mirror, so q is also negative. f = –8.00 cm q = –4.44 cm h’ = 2.50 cm Unknown: p = ? h = ?

37. Section 3 Curved Mirrors Chapter 13 Sample Problem, continued Convex Mirrors Diagram:

38. Section 3 Curved Mirrors Chapter 13 Sample Problem, continued Convex Mirrors 2. Plan Choose an equation or situation: Use the mirror equation and the magnification formula. Rearrange the equation to isolate the unknown:

39. Section 3 Curved Mirrors Chapter 13 Sample Problem, continued Convex Mirrors 3. Calculate Substitute the values into the equation and solve:

40. Section 3 Curved Mirrors Chapter 13 Sample Problem, continued Convex Mirrors 3. Calculate, continued Substitute the values for p and q to find the magnifi-cation of the image. Substitute the values for p, q, and h’ to find the height of the object.

41. Section 3 Curved Mirrors Chapter 13 Ray Tracing for a Convex Spherical Mirror

42. Section 3 Curved Mirrors Chapter 13 Parabolic Mirrors • Images created by spherical mirrors suffer from spherical aberration. • Spherical aberration occurs when parallel raysfar from the principal axisconverge away from the mirrors focal point. • Parabolic mirrors eliminate spherical aberration. All parallel rays converge at the focal point of a parabolic mirror.

43. Section 3 Curved Mirrors Chapter 13 Spherical Aberration and Parabolic Mirrors

44. Section 3 Curved Mirrors Chapter 13 Reflecting Telescope

45. Section 4 Color and Polarization Chapter 13 Objectives • Recognizehow additive colors affect the color of light. • Recognizehow pigments affect the color of reflected light. • Explainhow linearly polarized light is formed and detected.

46. Section 4 Color and Polarization Chapter 13 Color • Additive primary colorsproduce white light when combined. • Light of different colors can be produced by adding light consisting of theprimaryadditivecolors(red, green, and blue).

47. Section 4 Color and Polarization Chapter 13 Additive Color Mixing

48. Section 4 Color and Polarization Chapter 13 Color, continued • Subtractive primary colors filter out all light when combined. • Pigmentscan be produced by combining subtractive colors (magenta, yellow, and cyan).

49. Section 4 Color and Polarization Chapter 13 Subtractive Color Mixing

50. Section 4 Color and Polarization Chapter 13 Polarization of Light Waves • Linear polarizationis the alignment of electro-magnetic waves in such a way that the vibrations of the electric fields in each of the waves are parallel to each other. • Light can be linearly polarized through transmission. • The line along which light is polarized is called thetransmission axis of that substance.