2. MAP TAP 2003-2004The Electromagnetic Spectrum1 Light and the Electromagnetic Spectrum Chapters 22 & 23

3. MAP TAP 2003-2004The Electromagnetic Spectrum2 LIGHT: What Is It? Light Energy –Atoms As atoms absorb energy, electrons jump up to a higher energy level. Electrons release light when falling down to the lower energy level. –Photons - bundles/packets of energy released when the electrons fall. Light: Stream of photons © 2000 Microsoft Clip Gallery

4. MAP TAP 2003-2004The Electromagnetic Spectrum3 An electromagnetic wave consists of electric and magnetic fields which vibrate thus making waves. Energy is perpendicular to direction of motion Moving photon creates electric & magnetic field which are at right angles to each other. © 2000 Microsoft Clip Gallery

5. MAP TAP 2003-2004The Electromagnetic Spectrum4 LIGHT: Particles or Waves? Wave Model of Light –Explains most properties of light Particle Theory of Light –Photoelectric Effect – Photons of light produce free electrons © 2000 Microsoft Clip Gallery

6. MAP TAP 2003-2004The Electromagnetic Spectrum5 Light Waves Properties of light waves include speed, frequency and wavelength Speed (s), frequency (f) and wavelength ( ) are related in the formula x f = s All EM waves travel at a speed of 300,000 km/s in a vacuum EM waves will travel at slower speeds through medium such as air, water and glass

7. MAP TAP 2003-2004The Electromagnetic Spectrum6 Wavelength, Frequency and Energy Light with a short wavelength will have a high frequency and high energy. Light with long wavelengths have low frequencies and low energy

8. MAP TAP 2003-2004The Electromagnetic Spectrum7 Chapter 22 Section 2 The Electromagnetic Spectrum

9. MAP TAP 2003-2004The Electromagnetic Spectrum8

10. MAP TAP 2003-2004The Electromagnetic Spectrum9 Electromagnetic Spectrum The electromagnetic spectrum is the complete spectrum or continuum of light including radio waves, infrared, visible light, ultraviolet light, X- rays and gamma rays

11. MAP TAP 2003-2004The Electromagnetic Spectrum10

12. MAP TAP 2003-2004The Electromagnetic Spectrum11 Radio waves Low energy waves with long wavelengths and low frequencies Includes FM, AM, radar and TV waves Used in many devices such as remote control items, cell phones, wireless devices, etc. AM has longer wavelength, is used for audio portion of TV broadcasts and its long wavelength can bend around hills.

13. MAP TAP 2003-2004The Electromagnetic Spectrum12 Modulating Radio Waves Modulation – variation of amplitude or frequency when waves are broadcast AM – amplitude modulation FM - frequency modulation

14. MAP TAP 2003-2004The Electromagnetic Spectrum13 AM and FM AM – carries audio for TV broadcasts and its longer wavelengths bend around hills and tall buildings FM – carries video for TV broadcasts

15. MAP TAP 2003-2004The Electromagnetic Spectrum14

16. MAP TAP 2003-2004The Electromagnetic Spectrum15 Microwaves First used in radar, now used in communication, medicine and consumer use (microwave ovens)

17. MAP TAP 2003-2004The Electromagnetic Spectrum16 Infrared waves Invisible electromagnetic waves that are detected as heat Can be detected with special devices such as night goggles Used in heat lamps

18. MAP TAP 2003-2004The Electromagnetic Spectrum17

19. MAP TAP 2003-2004The Electromagnetic Spectrum18 Visible Light The portion of the electromagnetic spectrum that human eyes can detect ROY G BIV (red, orange, yellow, green, blue, indigo, violet) Red is the lowest frequency and violet is the highest frequency

20. MAP TAP 2003-2004The Electromagnetic Spectrum19

21. MAP TAP 2003-2004The Electromagnetic Spectrum20 Ultraviolet waves Higher energy than light waves Can cause skin cancer and blindness in humans Used in tanning beds, food processing and sterilizing equipment in hospitals, food processing Helps your body absorb Vitamin D

22. MAP TAP 2003-2004The Electromagnetic Spectrum21 X-Rays High energy waves First discovered by Roentgen Used in medicine, industry and astronomy Can cause cancer Bones absorb x-rays but soft tissue does not Lead absorbs X-rays

23. MAP TAP 2003-2004The Electromagnetic Spectrum22 Gamma rays Highest energy Shortest wavelength Come from outer space Blocked from Earth’s surface by atmosphere Can be used in cancer treatments

24. MAP TAP 2003-2004The Electromagnetic Spectrum23

25. MAP TAP 2003-2004The Electromagnetic Spectrum24 Time to think….. 1. What is the relationship between frequency and wavelength? 2. What is meant by ‘spectrum’? 3. What does ROY G BIV mean?

26. MAP TAP 2003-2004The Electromagnetic Spectrum25 Now, let’s really think 4. Can you actually see x-rays? –Support your answer. 5. Which color is more energetic, red or yellow? 6. Which type of wave travels faster, gamma or radio? 7. Why are microwaves more dangerous than radio waves?

27. MAP TAP 2003-2004The Electromagnetic Spectrum26 Think about it…. You have just been involved in a traffic incident that leaves you stranded on the side of the road. Which part of the electromagnetic spectrum would be of the most use to you and why?

28. MAP TAP 2003-2004The Electromagnetic Spectrum27 Answers 1. Frequency and wavelength are properties of waves and since speed is constant for EM waves, as frequency increases, wavelength decreases. 2. Spectrum is a continuum of all electromagnetic waves 3, ROY G BIV is the difference colors of the visible light in order of longest wavelength to shortest wavelength. 4. X-rays can not be seen, only the waves in the visible light portion are visible. 5. Yellow is higher energy than red because it has a shorter wavelength and higher frequency. 6. Both travel at the same speed, 300,000 km/s (all em waves travel at the same speed) 7. Microwaves have a higher frequency than radio and carry more energy.

29. MAP TAP 2003-2004The Electromagnetic Spectrum28 Chapter 22 Section 3 Interactions of Light

30. MAP TAP 2003-2004The Electromagnetic Spectrum29 Refraction of Light Refraction – Bending of light due to a change in speed. –Index of Refraction – Amount by which a material refracts light. –Prisms – Glass that bends light. Different frequencies are bent different amounts & light is broken out into different colors.

31. MAP TAP 2003-2004The Electromagnetic Spectrum30 Refraction – bending of light

32. MAP TAP 2003-2004The Electromagnetic Spectrum31 Diffraction & Refraction Diffraction – Bending of waves around the edge of a barrier. New waves are formed from the original. breaks images into bands of light & dark and colors. Refraction – Bending of waves due to a change in speed through an object.

33. MAP TAP 2003-2004The Electromagnetic Spectrum32 LIGHT & USES: Diffraction A diffraction grating. Each space between the ruled grooves acts as a slit. The light bends around the edges and gets refracted. © 2000 Microsoft Encarta

34. MAP TAP 2003-2004The Electromagnetic Spectrum33 Reflection Reflection – Bouncing back of light waves –Regular reflection – mirrors smooth surfaces scatter light very little. Images are clear & exact. –Diffuse reflection – reflected light is scattered due to an irregular surface.

35. MAP TAP 2003-2004The Electromagnetic Spectrum34 Chapter 22 Section 4 Light and Color

36. MAP TAP 2003-2004The Electromagnetic Spectrum35 Color of Light Transparent Objects: –Light transmitted because of no scattering –Color transmitted is color you see. All other colors are absorbed. Translucent: –Light is scattered and transmitted some. Opaque: –Light is either reflected or absorbed. –Color of opaque objects is color it reflects. © 2000 Microsoft Clip Gallery

37. MAP TAP 2003-2004The Electromagnetic Spectrum36 Color of Light (Cont.) Color of Objects –White light is the presence of ALL the colors of the visible spectrum. –Black objects absorb ALL the colors and no light is reflected back. © 2000 Microsoft Clip Gallery

38. MAP TAP 2003-2004The Electromagnetic Spectrum37 Color of Light (Cont.) Primary Colors of Light –Three colors that can be mixed to produce any other colored light –Red + blue + green = white light Complimentary Colors of Light –Two complimentary colors combine to make white light-Magenta,Cyan,Yellow © 2000 Microsoft Clip Gallery

39. MAP TAP 2003-2004The Electromagnetic Spectrum38 Paint Pigments –Pigments absorb the frequency of light that you see –Primary pigments Yellow + cyan + magenta = black Primary pigments are compliments of the primary colors of light. © 2000 Microsoft Clip Gallery

40. MAP TAP 2003-2004The Electromagnetic Spectrum39 Complementary Pigments Green, blue, red Complimentary pigments are primary colors for light! © 2000 Microsoft Clip Gallery

41. MAP TAP 2003-2004The Electromagnetic Spectrum40 Chapter 23 Section 1 Mirrors and Lenses

42. MAP TAP 2003-2004The Electromagnetic Spectrum41 Enlarged – –Image is larger than actual object. Reduced – –Image is smaller than object. © 2000 Microsoft Clip Gallery

43. MAP TAP 2003-2004The Electromagnetic Spectrum42 Erect – –Image is right side up. Inverted – –Image is upside down. © 2000 Microsoft Clip Gallery

44. MAP TAP 2003-2004The Electromagnetic Spectrum43 L Real Image – –Image is made from “real” light rays that converge at a real focal point so the image is REAL –Can be projected onto a screen because light actually passes through the point where the image appears –Always inverted

45. MAP TAP 2003-2004The Electromagnetic Spectrum44 Virtual Image– –“Not Real” because it cannot be projected –Image only seems to be there!

46. MAP TAP 2003-2004The Electromagnetic Spectrum45 Mirrors –Optical Axis – Base line through the center of a mirror or lens –Focal Point – Point where reflected or refracted rays meet & image is formed –Focal Length – Distance between center of mirror/lens and focal point © 2000 Microsoft Clip Gallery

47. MAP TAP 2003-2004The Electromagnetic Spectrum46 Mirrors Plane Mirrors – Perfectly flat –Virtual – Image is “Not Real” because it cannot be projected –Erect – Image is right side up © 2000 Microsoft Clip Gallery

48. MAP TAP 2003-2004The Electromagnetic Spectrum47 –Convex Mirror Curves outward Enlarges images. –Use: Rear view mirrors, store security… CAUTION! Objects are closer than they appear! © 2000 Microsoft Clip Gallery

49. MAP TAP 2003-2004The Electromagnetic Spectrum48 Lenses Convex Lenses –Thicker in the center than edges. –Lens that converges (brings together) light rays. –Forms real images and virtual images depending on position of the object

50. MAP TAP 2003-2004The Electromagnetic Spectrum49 LIGHT & ITS USES: Lenses Convex Lenses Ray Tracing –Two rays usually define an image Ray #1: Light ray comes from top of object; travels parallel to optic axis; bends thru focal point. Focal Point Lens Object © 2000 D. L. Power

51. MAP TAP 2003-2004The Electromagnetic Spectrum50 LIGHT & ITS USES: Lenses Convex Lenses Ray Tracing –Two rays define an image Ray 2: Light ray comes from top of object & travels through center of lens. Ray #1 Ray #2 © 2000 D. L. Power

52. MAP TAP 2003-2004The Electromagnetic Spectrum51 Concave Lenses Lens that is thicker at the edges and thinner in the center. –Diverges light rays –All images are erect and reduced. © 2000 D. L. Power

53. MAP TAP 2003-2004The Electromagnetic Spectrum52 Chapter 23 Section 2 Light and Sight

54. MAP TAP 2003-2004The Electromagnetic Spectrum53

55. MAP TAP 2003-2004The Electromagnetic Spectrum54 How You See Retina – – Lens refracts light to converge on the retina. Nerves transmit the image Rods – –Nerve cells in the retina. Very sensitive to light & dark Cones – –Nerve cells help to see light/color © 2000 Microsoft Clip Gallery

56. MAP TAP 2003-2004The Electromagnetic Spectrum55 How You See Near Sighted – Eyeball is too long and image focuses in front of the retina Far Sighted – Eyeball is too short so image is focused behind the retina. © 2000 Microsoft Clip Gallery

57. MAP TAP 2003-2004The Electromagnetic Spectrum56 Eye is a convex lens Nearsightedness – Concave lenses expand focal lengths Farsightedness – Convex lenses shortens the focal length.

58. MAP TAP 2003-2004The Electromagnetic Spectrum57 Chapter 23 Section 3 Light and Technology

59. MAP TAP 2003-2004The Electromagnetic Spectrum58 LIGHT & ITS USES Sources of Light –Incandescent light – light produced by heating an object until it glows. © 2000 Microsoft Clip Gallery

60. MAP TAP 2003-2004The Electromagnetic Spectrum59 LIGHT & ITS USES Fluorescent Light – –Light produced by electron bombardment of gas molecules –Phosphors absorb photons that are created when mercury gas gets zapped with electrons. The phosphors glow & produce light. © 2000 Microsoft Clip Gallery

61. MAP TAP 2003-2004The Electromagnetic Spectrum60 LIGHT & ITS USES - Neon Neon light – neon inside glass tubes makes red light. Other gases make other colors. © 2000 Microsoft Clip Gallery

62. MAP TAP 2003-2004The Electromagnetic Spectrum61 LIGHT & USES: Optical Instruments Cameras Telescopes Microscopes © 2000 Microsoft Clip Gallery

63. MAP TAP 2003-2004The Electromagnetic Spectrum62 Telescopes Refracting telescopes – use two convex lenses Reflecting telescopes use a concave mirror to bounce the light to a plane mirror which reflects the light to a convex lenses

64. MAP TAP 2003-2004The Electromagnetic Spectrum63 LIGHT & USES: Optical Instruments LASERS –Acronym: Light Amplification by Stimulated Emission of Radiation –Coherent Light – Waves are in phase so it is VERY powerful & VERY intense.

65. MAP TAP 2003-2004The Electromagnetic Spectrum64 LIGHT & USES: Optical Instruments LASERS –Holography – Use of Lasers to create 3-D images –Fiber Optics – Light energy transferred through long, flexible fibers of glass/plastic –Uses – Communications, medicine, t.v. transmission, data processing.

66. MAP TAP 2003-2004The Electromagnetic Spectrum65 Polarized Light Light waves vibrate in only one plane or direction. Can cause glare. Be sure your sunglasses are polarized to reduce the glare.

67. MAP TAP 2003-2004The Electromagnetic Spectrum66 Communication Technology Cordless phone – phone & radio signals Cellular phone – mainly uses microwaves to send signals Satellite TV – uses microwaves Global Positioning System (GPS) – uses microwaves and satellite system (24) – need a signal from at least 4 satellites to find a location.