1. Reflection and Refraction

2. Most objects we see reflect light rather than emit their own light.
Reflection
Most objects we see reflect light rather than emit their own light.

3. Principle of Least Time
Fermat's principle - light travels in straight lines and will take the path of least time to strike mirror and reflect from point A to B A B
Wrong Path
True Path
MIRROR

4. Law of Reflection
“The angle of incidence equals the angle of reflection.”
This is true for both flat mirrors and curved mirrors.

5. Normal Line
Angle of Incidence
Angle of Reflection A = B
MIRROR

6. C F
Tangent
Normal
Incidence
Reflection

7. Types of Reflection
Specular Reflection - images seen on smooth surfaces (e.g. plane mirrors)
Diffuse Reflection - diffuse light coming from a rough surface (cannot see a reflection of yourself)

9. Locating the Image for Plane Mirrors
Draw the image the same distance behind the mirror as the object is in front.
Draw a connector line from each object to each image.
If the connector line passes through the mirror, the image will be seen.

10. A E D B C A C D E B Mirror Images
These lines are pointed to the only images that will be seen from each of the original locations (A-E) NOTE: No images will be seen from E A C D E B

12. Concave Mirrors

13. Light from Infinite Distance
Focuses at the focal point

14. Two Rules for Locating the Image for Concave Mirrors
Any incident ray traveling parallel to the principal axis on the way to the mirror will pass through the focal point upon reflection

15. C F

16. Two Rules for Concave Mirrors
Any incident ray traveling parallel to the principal axis on the way to the mirror will pass through the focal point upon reflection
Any incident ray passing through the focal point on the way to the mirror will travel parallel to the principal axis upon reflection

17. C F

18. C F

19. C F

20. C F
Virtual
Image

21. Real vs. Virtual Image
When a real image is formed, it still appears to an observer as though light is diverging from the real image location
only in the case of a real image, light is actually passing through the image location
Light does not actually pass through the virtual image location
it only appears to an observer as though the light was emanating from the virtual image location

22. C F
Real Image C F
Virtual Image

23. Will an image ever focus at a single point with a convex mirror?
Therefore, the images you see are virtual!

24. Refraction
Refraction is the bending of light when it passes from one transparent medium to another
This bending is caused by differences in the speed of light in the media

25. Normal
Line
More Dense
Less Dense

26. Normal
Line #1
Light Beam
Fast
AIR
Slow
WATER
AIR

27. Normal
Line
More Dense
Less Dense

28. Normal
Line #1
Light Beam
Fast
AIR
Slow
Normal
Line #2
WATER
Fast
AIR

29. Refraction Examples
Light slows down when it goes from air into water and bends toward the normal.
An Analogy: A car slows down when it goes from pavement onto gravel and turns toward the normal.
An Illusion : Fish in the water appear closer and nearer the surface.

30. http://cougar. slvhs. slv. k12. ca

31. Refraction
Observer
AIR
WATER
False Fish
True Fish

32. Atmospheric Refraction
Our atmosphere can bend light and create distorted images called mirages.

36. Lenses Work due to change of direction of light due to refraction
Diverging Lens
A lens that is thinner in the middle than at the edges, causing parallel light rays to diverge.
Converging Lens
A lens that is thicker in the middle and refracts parallel light rays passing through to a focus.

37. Diverging or Concave LensF
Diverging or Concave Lens

38. Converging or Convex LensF C F

39. Converging or Convex LensF C F

40. Converging or Convex LensF C F

41. Converging or Convex LensF C F

42. Converging or Convex LensF C F

43. Converging or Convex LensF C F

44. Converging or Convex LensF C F

45. Converging or Convex LensF C F

46. Converging or Convex LensF C F

47. Converging or Convex LensF C F

49. Total Internal Reflection...
…is the total reflection of light traveling in a medium when it strikes a surface of a less dense medium
sin θ = n2/n1

50. http://cougar. slvhs. slv. k12. ca

51. Total Internal Reflection
Refraction
Critical Angle
AIR
WATER 49
Total
Internal
Reflection
Light
Source

55. Fiber Optics Association
What Is Fiber Optics ?
Transmitting communications signals over hair thin strands of glass or plastic
Not a "new" technology
Concept a century old
Used commercially for last 25 years
The first commercial fiber optic installation was in for telephone signals in Chicago, installed in The first long distance networks were operational in the early 1980s. By 1985, most of todays basic technology was developed and being installed in the fiber optic networks that now handle virtually all long distance telecommunications.
FOTM, Chapter 2, DVVC, Chapter 10
Fiber Optics Association

56. Fiber Has More Capacity
This single fiber can carry more communications than the giant copper cable!
That tiny strand of optical fiber can carry more communications signals than the large copper cable in the background and over much longer distances.
The copper cable has about 1000 pairs of conductors. Each pair can only carry about 24 telephone conversations a distance of less than 3 miles.
The fiber cable carries more than 32,000 conversations hundreds or even thousands of miles before it needs regeneration. Then each fiber can simultaneously carry over 150 times more by transmitting at different colors (called wavelengths) of light.
The cost of transmitting a single phone conversation over fiber optics is only about 1% the cost of transmitting it over copper wire! That’s why fiber is the exclusive medium for long distance communications.
Fiber Optics Association

57. Fiber Optic Communications
Applications include
Telephones
Internet
LANs - local area networks
CATV - for video, voice and Internet connections
Utilities - management of power grid
Security - closed-circuit TV and intrusion sensors
Military - everywhere!
These are but a few of the applications of fiber optics, as we concentrate on communications. Fiber optics are also used for lighting, signs, sensors and visual inspection (medicine and non-destructive testing).
FOTM, Chapter 2, DVVC, Chapter 10
Fiber Optics Association

58. Fiber Optics Association
Why Use Fiber Optics?
Economics
Speed
Distance
Weight/size
Freedom from interference
Electrical isolation
Security
The biggest advantage of optical fiber is the fact it can transport more information longer distances in less time than any other communications medium. In addition, it is unaffected by the interference of electromagnetic radiation which makes it possible to transmit information and data with less noise and less error. Fiber is lighter than copper wires which makes it popular for aircraft and automotive applications. These advantages open up the doors for many other advantages that make the use of optical fiber the most logical choice in data transmission.
FOTM, Chapter 2, DVVC, Chapter 10
Fiber Optics Association

59. Fiber Optic Applications
Fiber is already used in:
> 90% of all long distance telephony
> 50% of all local telephony
Most CATV networks
Most LAN (computer network) backbones
Many video surveillance links
About the only place fiber has not become the dominant cable is desktop connections for LANs. Priced to just replace copper, it is more expensive, but using a centralized fiber architecture, fiber allows the removal of electronics from the telecom room and ends up being less expensive!
FOTM, Chapter 2, DVVC, Chapter 10
Fiber Optics Association

60. Fiber Optic Applications
Fiber is the least expensive, most reliable method for high speed and/or long distance communications
While we already transmit signals at Gigabits per second speeds, we have only started to utilize the potential bandwidth of fiber
Singlemode fiber used in telecommunications and CATV has a bandwidth of greater than a terahertz. Standard systems today carry up to 64 channels of 10 gigabit signals - each at a unique wavelength.
FOTM, Chapter 2, DVVC, Chapter 10
Fiber Optics Association

61. Fiber Optics Association
Fiber Technology
Optical fiber is comprised of a light carrying core surrounded by a cladding which traps the light in the core by the principle of total internal reflection. Most optical fibers are made of glass, although some are made of plastic. The core and cladding are usually fused silica glass which is covered by a plastic coating called the buffer or primary buffer coating which protects the glass fiber from physical damage and moisture. There are some all plastic fibers used for specific applications. Glass optical fibers are the most common type used in communication applications.
FOTM, Chapter 2, DVVC, Chapter 11
Fiber Optics Association

62. Fiber Optics Association
Fiber Technology
By making the core of the fiber of a material with a higher refractive index, we can cause the light in the core to be totally reflected at the boundary of the cladding for all light that strikes at greater than a critical angle determined by the difference in the composition of the materials used in the core and cladding.
Many students are curious how fiber is made. Good explanations are available in the FOTM, on the Fiber Optic Association website under “Tech Topics” and from most fiber manufacturers.
FOTM, Chapter 2, DVVC, Chapter 11
Fiber Optics Association

63. Fiber Optics Association
Fiber Optic Data Links
Fiber optic transmission systems all consist of a transmitter which takes an electrical input and converts it to an optical output from a laser diode or LED. The light from the transmitter is coupled into the fiber with a connector and is transmitted through the fiber optic cable plant.
The light is ultimately coupled to a receiver where a detector converts the light into an electrical signal which is then conditioned properly for use by the receiving equipment.
Just as with copper wire or radio transmission, the performance of the fiber optic data link can be determined by how well the reconverted electrical signal out of the receiver matches the input to the transmitter.
FOTM, Chapter 2, DVVC, Chapter 11
Fiber Optics Association

64. Light Used In Fiber Optics
Fiber optic systems transmit using infrared light, invisible to the human eye, because it goes further in the optical fiber at those wavelengths.
The ultra-pure glass used in making optical fiber has less attenuation (signal loss) at wavelengths (colors) in the infrared, beyond the limits of the sensitivity of the human eye. The fiber is designed to have the highest performance at these wavelengths.
The particular wavelengths used, 850, 1300 and 1550 nm, correspond to wavelengths where optical light sources (lasers or LEDs) are easily manufactured.
Some advanced fiber optic systems transmit light at several wavelengths at once through a single optical fiber to increase data throughput. We call this method “wavelength division multiplexing.”
Fiber Optics Association

65. Wavelength-Division Multiplexing
How Does Wavelength-Division Multiplexing (WDM) Work?
It is easy to understand WDM. Consider the fact that you can see many different colors of light - red, green, yellow, blue, etc., all at once. The colors are transmitted through the air together and may mix, but they can be easily separated using a simple device like a prism, just like we separate the "white" light from the sun into a spectrum of colors with the prism.
The input end of a WDM system is really quite simple. It is a simple coupler that combines or multiplexes all the signal inputs into one output fiber. The demultiplexer separates the light at the end of the fiber. It shines the light on a grating (a mirror like device that works like a prism and looks similar to the data side of a CD) which separates the light into the different wavelengths by sending them off at different angles. Optics capture each wavelength and focuses it into another fiber, creating separate outputs for each wavelength of light.
Current systems offer from 4 to 32 channels of wavelengths. The higher numbers of wavelengths has lead to the name “Dense” Wavelength Division Multiplexing or DWDM.
FOTM, Chapter 3, DVVC, Chapter 10
Fiber Optics Association

66. Fiber Optics Association
Fiber Optic Cable
Protects the fibers wherever they are installed
May have 1 to over 1000 fibers
Optical fibers are enclosed in cables for protection against the environment in which they are installed. Cables installed in trays in buildings require less protection than, for example, cables buried underground or placed under water.
Cables will include strength members, typically a strong synthetic fiber called aramid fiber or Kevlar for its duPont trade name, which takes the stress of pulling the cable. The thin yellow fibers in the photo are the strength members.
The outside of the cable is called the jacket. It is the final protection for the fibers and must withstand extremes of temperatures, moisture and the stress of installation. Some cables even have a layer of thin metal under the jacket to prevent rodents from chewing throught the cable.
The colors you see above are color-coding so you can identify individual fibers in the cable.
Fiber Optics Association

67. Fiber Optic Connectors
Terminates the fibers
Connects to other fibers or transmission equipment
When a fiber needs to be connected to another, it can be spliced permanently by “welding” it at high temperatures or with adhesives, or it can be terminated with a connector that makes it possible to handle the individual fiber without damage.
Connectors align two fibers the size of a human hair such that little light is lost. Most connectors use ceramic cylinders about 2.5 mm in diameter with precisely aligned holes in the center that accept the fiber. Most connectors use adhesive to attach the fiber and the end is polished to a smooth finish.
Putting connectors on the end of fibers is a job that requires patience, skill and good training. Fiber optic technicians are expected to be able to install connectors properly.

68. Medical Fiberscopes
Electromagnetic radiation has played a role in medicine for decades
Particularly interesting is the ability to gain information without invasive procedures
Using fiber optics in medicine has opened up new uses for lasers

69. Fiberscope Construction
Fiberscopes were the first use of optical fibers in medicine
Invented in 1957
The objective lens forms a real image on the end of the bundle of fiber optics
This image is carried to the other end of the bundle where an eyepiece is used to magnify the image

70. Endoscopes
An endoscope is a fiberscope with additional channels besides those for illuminating and viewing fibers
The uses of these extra channels may include
Introducing or withdrawing fluids
Vacuum suction
Scalpels for cutter or lasers for surgical applications

72. Air – Diamond Interface
sin θ = n2/n1
Air nair = 1 and Diamond n2 = 2.42
sin θ = 1.00/2.42 = 0.413
sin θ = 0.413
θ = sin
θ = 24o

73. http://cougar. slvhs. slv. k12. ca

74. Dispersion...
…is the separation of white light into pure colors (ROY G. BIV).
The index of refraction is higher for higher frequencies, so violet is bent the most
Dispersion Examples:
Prisms
Diffraction Gratings
CD’s
Raindrops

77. Rainbows Raindrops refract, reflect and disperse sunlight.
Rainbows will always appear opposite of the Sun in the sky.
You cannot run from or run to a rainbow!