WAVES: SOUND & LIGHT Waves carry energy from one place to another
NATURE OF WAVES <ul><li>Waves  (Def.)  – A wave is a disturbance that transfers energy. </li></ul><ul><li>Medium – Substan...
LIGHT: What Is It? <ul><li>Light Energy </li></ul><ul><ul><li>Atoms </li></ul></ul><ul><ul><ul><li>As atoms absorb energy,...
Electromagnetic Waves <ul><li>Speed in Vacuum </li></ul><ul><ul><li>300,000 km/sec </li></ul></ul><ul><ul><li>186,000 mi/s...
Transverse Waves <ul><li>Energy is perpendicular to direction of motion </li></ul><ul><li>Moving photon creates electric &...
Electromagnetic Spectrum © 2000 Microsoft Clip Gallery
Electromagnetic Spectrum <ul><li>Visible Spectrum – Light we can see </li></ul><ul><ul><li>Roy G. Biv – Acronym for  Red ,...
Electromagnetic Spectrum <ul><li>Invisible Spectrum </li></ul><ul><ul><li>Radio Waves </li></ul></ul><ul><ul><ul><li>Def. ...
Modulating Radio Waves <ul><li>Modulation - variation of amplitude or frequency when waves are broadcast </li></ul><ul><ul...
Short Wavelength Microwave <ul><li>Invisible Spectrum (Cont.) </li></ul><ul><ul><li>Infrared Rays </li></ul></ul><ul><ul><...
Electromagnetic Spectrum <ul><li>Invisible spectrum (cont.). </li></ul><ul><ul><li>Ultraviolet rays. </li></ul></ul><ul><u...
Electromagnetic Spectrum  <ul><li>Invisible Spectrum (Cont.) </li></ul><ul><ul><li>X-Rays </li></ul></ul><ul><ul><ul><li>D...
Electromagnetic Spectrum <ul><li>Invisible spectrum (cont.) </li></ul><ul><ul><li>Gamma rays </li></ul></ul><ul><ul><ul><l...
LIGHT: Particles or Waves? <ul><li>Wave Model of Light </li></ul><ul><ul><li>Explains most properties of light </li></ul><...
LIGHT: Refraction of Light <ul><li>Refraction – Bending of light due to a change in speed.  </li></ul><ul><ul><li>Index of...
Color of Light <ul><li>Transparent Objects:  </li></ul><ul><ul><li>Light transmitted because of no scattering </li></ul></...
Color of Light (Cont.) <ul><li>Color of Objects </li></ul><ul><ul><li>White light is the presence of ALL the colors of the...
How You See <ul><li>Retina –  </li></ul><ul><ul><li>Lens refracts light to converge on the retina.  Nerves transmit the im...
Refraction (Cont.)
Geometry Refresher A B   C parallel lines given A:      
Electrical Component Magnetic Component Electromagnetic Wave In optics ignore magnetic component
Wavelength and Frequency Wavelength:  Distance between adjacent troughs or crests   nm (10 -9  m) Frequency:  Number of ...
Speed of light  in vacuum ,  C  = 3 x 10 8  m/sec Speed is slower in matter Air New Medium Speed =  C Speed =  V
medium 1 medium 2 n 1 n 2 REFRACTION Snell’s Law:  n 1 sin    n 2 sin     angle of incidence   angle of refract...
Snell’s Law n 1   sin       = n 2  sin     n 1  = 1.00 30 o n 2  = 1.50 ? o 19.47 o
Willebrord van Roijen Snell 1580 - 1626 Professor of Mathematics University of Leiden, Netherlands
lower  n higher  n Ray bends toward normal Which way do the rays bend in refraction?
higher   n lower  n Ray bends away from normal
Atmospheric Refraction and Mirages <ul><li>A mirage can be observed when the air above the ground is warmer than the air a...
Reflection and Refraction Light is reflected as well as refracted at surfaces. refracted ray reflected ray n n’  i  r n’...
Reflection  <ul><li>Reflection – Bouncing back of light waves </li></ul><ul><ul><li>Regular reflection – mirrors smooth su...
Reflection Vocabulary <ul><li>Enlarged –  </li></ul><ul><ul><li>Image is larger than actual object. </li></ul></ul><ul><li...
Reflection Vocabulary <ul><ul><li>Focal Point – Point where reflected or refracted rays meet & image is formed </li></ul><...
Notations <ul><li>The distance from the object to the lens is denoted by  D o </li></ul><ul><li>The distance from the imag...
Types of Images for Mirrors and Lenses <ul><li>A  real image  is one in which  light actually passes through  the image po...
Flat Mirror <ul><li>Simplest possible mirror </li></ul><ul><li>Properties of the image can be determined by geometry </li>...
Properties of the Image Formed by a Flat Mirror <ul><li>The image is as far behind the mirror as the object is in front </...
Application – Day and Night Settings on Car Mirrors <ul><li>With the daytime setting, the bright beam of reflected light i...
Spherical Mirrors <ul><li>A  spherical mirror  has the shape of a segment of a sphere </li></ul><ul><li>A  concave  spheri...
LIGHT & ITS USES:  Mirrors <ul><li>Convex Mirror </li></ul><ul><ul><ul><li>A  convex  mirror is sometimes called a  diverg...
Concave Mirror,  D o  >  F <ul><li>The image is real </li></ul><ul><li>The image is inverted </li></ul><ul><li>The image i...
Concave Mirror,  D o  <  F <ul><li>The image is virtual </li></ul><ul><li>The image is upright </li></ul><ul><li>The image...
Convex Mirror <ul><li>The image is virtual </li></ul><ul><li>The image is upright </li></ul><ul><li>The image is smaller <...
Drawing A Ray Diagram <ul><li>To make the ray diagram, you need to know </li></ul><ul><ul><li>The position of the object <...
Sign Conventions for Lenses Diverging Lens Converging Lens Focal Length (f) (1/2 Radius of Curvature, C)  Image is inverte...
Focal Length of a Converging Lens <ul><li>The  parallel rays  pass through the lens and  converge  at the focal point  F <...
Focal Length of a Diverging Lens <ul><li>The  parallel rays diverge  after passing through the diverging lens </li></ul><u...
LIGHT & ITS USES: Lenses <ul><li>Convex Lenses  </li></ul><ul><ul><li>Thicker in the center than edges.  </li></ul></ul><u...
LIGHT & ITS USES: Lenses <ul><li>Convex Lenses  </li></ul><ul><li>Ray Tracing </li></ul><ul><ul><li>Two rays usually defin...
LIGHT & ITS USES: Lenses <ul><li>Convex Lenses  </li></ul><ul><li>Ray Tracing </li></ul><ul><ul><li>Two rays define an ima...
LIGHT & ITS USES: Lenses <ul><li>Concave Lenses –  </li></ul><ul><ul><li>Lens that is thicker at the edges and thinner in ...
How You See  <ul><li>Near Sighted – Eyeball is too long and image focuses in front of the retina </li></ul><ul><li>Far Sig...
LIGHT & USES: Lenses <ul><li>Concave Lenses –  </li></ul><ul><ul><li>Vision – Eye is a convex lens. </li></ul></ul><ul><ul...
LIGHT & USES:  Optical Instruments <ul><li>Cameras </li></ul><ul><li>Telescopes </li></ul><ul><li>Microscopes </li></ul>© ...
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E M Spectrum Snell S Law And Ray Diagrams

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E M Spectrum Snell S Law And Ray Diagrams

  1. 1. WAVES: SOUND & LIGHT Waves carry energy from one place to another
  2. 2. NATURE OF WAVES <ul><li>Waves (Def.) – A wave is a disturbance that transfers energy. </li></ul><ul><li>Medium – Substance or region through which a wave is transmitted. </li></ul><ul><li>Speed of Waves – Depends on the properties of the medium. </li></ul>
  3. 3. LIGHT: What Is It? <ul><li>Light Energy </li></ul><ul><ul><li>Atoms </li></ul></ul><ul><ul><ul><li>As atoms absorb energy, electrons jump out to a higher energy level. </li></ul></ul></ul><ul><ul><ul><li>Electrons release light when falling down to the lower energy level. </li></ul></ul></ul><ul><ul><li>Photons - bundles/packets of energy released when the electrons fall. </li></ul></ul><ul><li>Light: Stream of Photons </li></ul>© 2000 Microsoft Clip Gallery © 2000 Microsoft Clip Gallery
  4. 4. Electromagnetic Waves <ul><li>Speed in Vacuum </li></ul><ul><ul><li>300,000 km/sec </li></ul></ul><ul><ul><li>186,000 mi/sec </li></ul></ul><ul><li>Speed in Other Materials </li></ul><ul><ul><li>Slower in Air, Water, Glass </li></ul></ul>© 2000 Microsoft Clip Gallery
  5. 5. Transverse Waves <ul><li>Energy is perpendicular to direction of motion </li></ul><ul><li>Moving photon creates electric & magnetic field </li></ul><ul><ul><li>Light has BOTH Electric & Magnetic fields at right angles! </li></ul></ul>© 2000 Microsoft Clip Gallery
  6. 6. Electromagnetic Spectrum © 2000 Microsoft Clip Gallery
  7. 7. Electromagnetic Spectrum <ul><li>Visible Spectrum – Light we can see </li></ul><ul><ul><li>Roy G. Biv – Acronym for Red , Orange , Yellow , Green , Blue , Indigo , & Violet. </li></ul></ul><ul><ul><li>Largest to Smallest Wavelength. </li></ul></ul>
  8. 8. Electromagnetic Spectrum <ul><li>Invisible Spectrum </li></ul><ul><ul><li>Radio Waves </li></ul></ul><ul><ul><ul><li>Def. – Longest wavelength & lowest frequency. </li></ul></ul></ul><ul><ul><ul><li>Uses – Radio & T.V. broadcasting. </li></ul></ul></ul>© 2000 Microsoft Clip Gallery
  9. 9. Modulating Radio Waves <ul><li>Modulation - variation of amplitude or frequency when waves are broadcast </li></ul><ul><ul><li>AM – amplitude modulation </li></ul></ul><ul><ul><ul><li>Carries audio for T.V. Broadcasts </li></ul></ul></ul><ul><ul><ul><li>Longer wavelength so can bend around hills </li></ul></ul></ul><ul><ul><li>FM – frequency modulation </li></ul></ul><ul><ul><ul><li>Carries video for T.V. Broadcasts </li></ul></ul></ul>© 2000 Microsoft Clip Gallery
  10. 10. Short Wavelength Microwave <ul><li>Invisible Spectrum (Cont.) </li></ul><ul><ul><li>Infrared Rays </li></ul></ul><ul><ul><ul><li>Def – Light rays with longer wavelength than red light. </li></ul></ul></ul><ul><ul><ul><li>Uses: Cooking, Medicine, T.V. remote controls </li></ul></ul></ul>
  11. 11. Electromagnetic Spectrum <ul><li>Invisible spectrum (cont.). </li></ul><ul><ul><li>Ultraviolet rays. </li></ul></ul><ul><ul><ul><li>Def. – EM waves with frequencies slightly higher than visible light </li></ul></ul></ul><ul><ul><ul><li>Uses: food processing & hospitals to kill germs’ cells </li></ul></ul></ul><ul><ul><ul><li>Helps your body use vitamin D. </li></ul></ul></ul>
  12. 12. Electromagnetic Spectrum <ul><li>Invisible Spectrum (Cont.) </li></ul><ul><ul><li>X-Rays </li></ul></ul><ul><ul><ul><li>Def. - EM waves that are shorter than UV rays. </li></ul></ul></ul><ul><ul><ul><li>Uses: Medicine – Bones absorb x-rays; soft tissue does not. </li></ul></ul></ul><ul><ul><ul><li>Lead absorbs X-rays. </li></ul></ul></ul>
  13. 13. Electromagnetic Spectrum <ul><li>Invisible spectrum (cont.) </li></ul><ul><ul><li>Gamma rays </li></ul></ul><ul><ul><ul><li>Def. Highest frequency EM waves; Shortest wavelength. They come from outer space. </li></ul></ul></ul><ul><ul><ul><li>Uses: cancer treatment. </li></ul></ul></ul>
  14. 14. LIGHT: Particles or Waves? <ul><li>Wave Model of Light </li></ul><ul><ul><li>Explains most properties of light </li></ul></ul><ul><li>Particle Theory of Light </li></ul><ul><ul><li>Photoelectric Effect – Photons of light produce free electrons </li></ul></ul>© 2000 Microsoft Clip Gallery
  15. 15. LIGHT: Refraction of Light <ul><li>Refraction – Bending of light due to a change in speed. </li></ul><ul><ul><li>Index of Refraction – Amount by which a material refracts light. </li></ul></ul><ul><ul><li>Prisms – Glass that bends light. Different frequencies are bent different amounts & light is broken out into different colors. </li></ul></ul>
  16. 16. Color of Light <ul><li>Transparent Objects: </li></ul><ul><ul><li>Light transmitted because of no scattering </li></ul></ul><ul><ul><li>Color transmitted is color you see. All other colors are absorbed . </li></ul></ul><ul><li>Translucent: </li></ul><ul><ul><li>Light is scattered and transmitted some. </li></ul></ul><ul><li>Opaque: </li></ul><ul><ul><li>Light is either reflected or absorbed. </li></ul></ul><ul><ul><li>Color of opaque objects is color it reflects. </li></ul></ul>© 2000 Microsoft Clip Gallery
  17. 17. Color of Light (Cont.) <ul><li>Color of Objects </li></ul><ul><ul><li>White light is the presence of ALL the colors of the visible spectrum. </li></ul></ul><ul><ul><li>Black objects absorb ALL the colors and no light is reflected back. </li></ul></ul>© 2000 Microsoft Clip Gallery
  18. 18. How You See <ul><li>Retina – </li></ul><ul><ul><li>Lens refracts light to converge on the retina. Nerves transmit the image </li></ul></ul><ul><li>Rods – </li></ul><ul><ul><li>Nerve cells in the retina. Very sensitive to light & dark </li></ul></ul><ul><li>Cones – </li></ul><ul><ul><li>Nerve cells help to see light/color </li></ul></ul>© 2000 Microsoft Clip Gallery
  19. 19. Refraction (Cont.)
  20. 20. Geometry Refresher A B   C parallel lines given A:      
  21. 21. Electrical Component Magnetic Component Electromagnetic Wave In optics ignore magnetic component
  22. 22. Wavelength and Frequency Wavelength: Distance between adjacent troughs or crests   nm (10 -9 m) Frequency: Number of times cycle repeats per second f Hz ( sec -1 ) Speed = Frequency X Wavelength v = f 
  23. 23. Speed of light in vacuum , C = 3 x 10 8 m/sec Speed is slower in matter Air New Medium Speed = C Speed = V
  24. 24. medium 1 medium 2 n 1 n 2 REFRACTION Snell’s Law: n 1 sin    n 2 sin     angle of incidence   angle of refraction
  25. 25. Snell’s Law n 1 sin   = n 2 sin   n 1 = 1.00 30 o n 2 = 1.50 ? o 19.47 o
  26. 26. Willebrord van Roijen Snell 1580 - 1626 Professor of Mathematics University of Leiden, Netherlands
  27. 27. lower n higher n Ray bends toward normal Which way do the rays bend in refraction?
  28. 28. higher n lower n Ray bends away from normal
  29. 29. Atmospheric Refraction and Mirages <ul><li>A mirage can be observed when the air above the ground is warmer than the air at higher elevations </li></ul><ul><li>The rays in path B are directed toward the ground and then bent by refraction </li></ul><ul><li>The observer sees both an upright and an inverted image </li></ul>
  30. 30. Reflection and Refraction Light is reflected as well as refracted at surfaces. refracted ray reflected ray n n’  i  r n’ > n incident ray  i =  r
  31. 31. Reflection <ul><li>Reflection – Bouncing back of light waves </li></ul><ul><ul><li>Regular reflection – mirrors smooth surfaces scatter light very little. Images are clear & exact. </li></ul></ul><ul><ul><li>Diffuse reflection – reflected light is scattered due to an irregular surface. </li></ul></ul>
  32. 32. Reflection Vocabulary <ul><li>Enlarged – </li></ul><ul><ul><li>Image is larger than actual object. </li></ul></ul><ul><li>Reduced – </li></ul><ul><ul><li>Image is smaller than object. </li></ul></ul><ul><li>Upright – </li></ul><ul><ul><li>Image is right side up. </li></ul></ul><ul><li>Inverted – </li></ul><ul><ul><li>Image is upside down. </li></ul></ul>
  33. 33. Reflection Vocabulary <ul><ul><li>Focal Point – Point where reflected or refracted rays meet & image is formed </li></ul></ul><ul><ul><li>Focal Length – Distance between center of mirror/lens and focal point </li></ul></ul>
  34. 34. Notations <ul><li>The distance from the object to the lens is denoted by D o </li></ul><ul><li>The distance from the image to the lens is denoted by D i </li></ul><ul><li>The lateral magnification of the lens is the ratio of the image height ( h ’) to the object height ( h ) </li></ul><ul><ul><li>Denoted by M (= h’ / h ) </li></ul></ul>
  35. 35. Types of Images for Mirrors and Lenses <ul><li>A real image is one in which light actually passes through the image point </li></ul><ul><ul><li>Real images can be displayed on screens </li></ul></ul><ul><li>A virtual image is one in which the light does not pass through the image point </li></ul><ul><ul><li>The light appears to come (diverge) from that point </li></ul></ul><ul><ul><li>Virtual images cannot be displayed on screens </li></ul></ul>
  36. 36. Flat Mirror <ul><li>Simplest possible mirror </li></ul><ul><li>Properties of the image can be determined by geometry </li></ul><ul><li>One ray starts at P , follows path PQ and reflects back on itself </li></ul><ul><li>A second ray follows path PR and reflects according to the Law of Reflection </li></ul>Di = Do
  37. 37. Properties of the Image Formed by a Flat Mirror <ul><li>The image is as far behind the mirror as the object is in front </li></ul><ul><ul><li>Di = Do </li></ul></ul><ul><li>The image is unmagnified, M =1 </li></ul><ul><li>The image is virtual </li></ul><ul><li>The image is upright </li></ul><ul><ul><li>It has the same orientation as the object </li></ul></ul><ul><li>There is an apparent left-right reversal in the image </li></ul>
  38. 38. Application – Day and Night Settings on Car Mirrors <ul><li>With the daytime setting, the bright beam of reflected light is directed into the driver’s eyes </li></ul><ul><li>With the nighttime setting, the dim beam ( D ) of reflected light is directed into the driver’s eyes, while the bright beam goes elsewhere </li></ul>
  39. 39. Spherical Mirrors <ul><li>A spherical mirror has the shape of a segment of a sphere </li></ul><ul><li>A concave spherical mirror has the silvered surface of the mirror on the inner, or concave, side of the curve </li></ul><ul><li>A convex spherical mirror has the silvered surface of the mirror on the outer, or convex, side of the curve </li></ul>
  40. 40. LIGHT & ITS USES: Mirrors <ul><li>Convex Mirror </li></ul><ul><ul><ul><li>A convex mirror is sometimes called a diverging mirror </li></ul></ul></ul><ul><ul><ul><li>Curves outward </li></ul></ul></ul><ul><ul><ul><li>Reduces images. </li></ul></ul></ul><ul><ul><li>Use: Rear view mirrors, store security… </li></ul></ul>CAUTION! Objects are closer than they appear!
  41. 41. Concave Mirror, D o > F <ul><li>The image is real </li></ul><ul><li>The image is inverted </li></ul><ul><li>The image is smaller </li></ul><ul><li>than the object </li></ul>
  42. 42. Concave Mirror, D o < F <ul><li>The image is virtual </li></ul><ul><li>The image is upright </li></ul><ul><li>The image is larger </li></ul><ul><li>than the object </li></ul>
  43. 43. Convex Mirror <ul><li>The image is virtual </li></ul><ul><li>The image is upright </li></ul><ul><li>The image is smaller </li></ul><ul><li>than the object </li></ul>
  44. 44. Drawing A Ray Diagram <ul><li>To make the ray diagram, you need to know </li></ul><ul><ul><li>The position of the object </li></ul></ul><ul><ul><li>The position of the center of curvature </li></ul></ul><ul><li>Three rays are drawn </li></ul><ul><ul><li>They all start from the same position on the object </li></ul></ul><ul><li>The intersection of any two of the rays at a point locates the image </li></ul><ul><ul><li>The third ray serves as a check of the construction </li></ul></ul><ul><li>A ray diagram can be used to determine the position and size of an image </li></ul>
  45. 45. Sign Conventions for Lenses Diverging Lens Converging Lens Focal Length (f) (1/2 Radius of Curvature, C) Image is inverted Image is upright Image height ( h ’) Image is in front of surface (virtual) Image is in back of surface (real) Image location ( Di ) Object is in back of surface Object is in front of surface Object location ( Do ) Negative When Positive When Quantity
  46. 46. Focal Length of a Converging Lens <ul><li>The parallel rays pass through the lens and converge at the focal point F </li></ul><ul><li>The parallel rays can come from the left or right of the lens </li></ul><ul><li>f is positive </li></ul>
  47. 47. Focal Length of a Diverging Lens <ul><li>The parallel rays diverge after passing through the diverging lens </li></ul><ul><li>The focal point is the point where the rays appear to have originated </li></ul><ul><li>f is negative </li></ul>
  48. 48. LIGHT & ITS USES: Lenses <ul><li>Convex Lenses </li></ul><ul><ul><li>Thicker in the center than edges. </li></ul></ul><ul><ul><li>Lens that converges (brings together) light rays. </li></ul></ul><ul><ul><li>Forms real images and virtual images depending on position of the object </li></ul></ul>
  49. 49. LIGHT & ITS USES: Lenses <ul><li>Convex Lenses </li></ul><ul><li>Ray Tracing </li></ul><ul><ul><li>Two rays usually define an image </li></ul></ul><ul><ul><ul><li>Ray #1: Light ray comes from top of object; travels parallel to optic axis; bends thru focal point. </li></ul></ul></ul>Focal Point Lens Object © 2000 D. L. Power
  50. 50. LIGHT & ITS USES: Lenses <ul><li>Convex Lenses </li></ul><ul><li>Ray Tracing </li></ul><ul><ul><li>Two rays define an image </li></ul></ul><ul><ul><ul><li>Ray 2: Light ray comes from top of object & travels through center of lens. </li></ul></ul></ul>Ray #1 Ray #2 © 2000 D. L. Power
  51. 51. LIGHT & ITS USES: Lenses <ul><li>Concave Lenses – </li></ul><ul><ul><li>Lens that is thicker at the edges and thinner in the center. </li></ul></ul><ul><ul><li>Diverges light rays </li></ul></ul><ul><ul><li>All images are upright and reduced. </li></ul></ul>© 2000 D. L. Power
  52. 52. How You See <ul><li>Near Sighted – Eyeball is too long and image focuses in front of the retina </li></ul><ul><li>Far Sighted – Eyeball is too short so image is focused behind the retina. </li></ul>© 2000 Microsoft Clip Gallery © 2000 Microsoft Clip Gallery
  53. 53. LIGHT & USES: Lenses <ul><li>Concave Lenses – </li></ul><ul><ul><li>Vision – Eye is a convex lens. </li></ul></ul><ul><ul><ul><li>Nearsightedness – Concave lenses expand focal lengths </li></ul></ul></ul><ul><ul><ul><li>Farsightedness – Convex lenses shortens the focal length. </li></ul></ul></ul>
  54. 54. LIGHT & USES: Optical Instruments <ul><li>Cameras </li></ul><ul><li>Telescopes </li></ul><ul><li>Microscopes </li></ul>© 2000 Microsoft Clip Gallery © 2000 Microsoft Clip Gallery © 2000 Microsoft Clip Gallery

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