1.  Optics Chapter 4: Many properties of light can be understood using a wave model of light.

2. The History of Light  Pythagoras  A Greek philosopher  Believed that beams of light were made of tiny particles.  The eyes detected these particles and could see the object.

3. Galileo  Galileo is believed to be the first person to try and measure the speed of light.  He and an assistant stood on hilltops about one kilometer apart holding lanterns.  He would uncover his lantern first and as soon as his assistant saw the light he would uncover his lantern.  Galileo would then measure the time between the moment that he saw the light from his assistants lantern.  He was unable to calculate the speed of light from his results.

4. Albert Michelson  First person to measure the speed of light (3 x 10 8 m/s)

5. Speed: Light vs. Sound  Light 1 000 000 000 km/h  Sound 1 200 km/h

6. Thunder and Lightning

7.  Both the lightning strike and the roar of thunder happen at the same time.  You see the lightning first.  If you multiply the time in seconds between the strike and the roar by the speed of sound, you will find the approximate distance.

8. Orion’s Belt  The light takes thousands of years to reach our eyes.

9. Light Technologies Include…  Microscope  Telescope  Periscope  Binoculars  Fibre Optics  Camera

10.  Prescription contact lenses  Laser  Movie Projectors  Overhead Projectors

11. Properties of Waves  A wave transfers energy through matter or space.

12. The Wave Model  Explains that light is a type of wave that travels through empty space and transfers energy from one place to another.

13. A Wave… A Peak is also called the crest and is the highest part of the wave. Trough = the lowest point in the wave. 1. Wavelength 2. Amplitude 3. Crest 4. Trough

14. Frequency  Frequency: the number of repetitive motions that occur during a given time.  Ex: the number of wavelengths that pass a point in 1 second.  Measured in Hertz

15. Amplitude  Amplitude: the height of a wave crest or the depth of a wave trough as measured from rest position.  Crest height = trough depth  The larger the amplitude the greater the energy transported.

16. Wavelength  Wavelength: the distance from crest to crest, trough to trough or the distance covered by one complete crest and one complete trough.  Measured in: meters.  Longer wavelengths refract the least.

17. Frequency & Wavelength  High frequency waves have short wavelengths.  Low Frequency waves have long wavelengths.

18. Transverse Wave  Transverse Wave: matter in the medium moves up and down perpendicular to the direction that the wave travels.  Example: When you shake one end of a rope while your friend holds the other end.  The wave travels from you to your friend.  The rope moves up and down.

19. Compression Wave  Compression Wave: matter in medium moves back and forth along the same direction that the wave travels.  Example: Squeeze several coils of a spring together at one end of the spring. Then let go of coils (while still holding onto the end). A wave will move along the spring.

20. Waves

21. Light  Light: a form of energy that can be detected by the human eye.  Visible Light: a mixture of all the colors of the rainbow.

22. Properties of Visible Light 1: Light Travels in a straight line.  ( rectilinear propagation)

23. 2: Light Reflects (reflection)

24. 3: Light refracts. (refraction)

25. 4: Light Disperses (Dispersion)

26. 5: Light travels through a vacuum (does not require a medium; no particles involved)

27. 6: Travels through objects at different degrees. https://www.youtube.com/wa tch?v=ldGWaLRIL4Y http://studyjams.scholastic.co m/studyjams/jams/science/ene rgy-light-sound/light-absorb- reflect-refract.htm

28. Visible Light Spectrum  Can be seen due to the dispersion of light through a prism.

29. The constituent colors of white light are:  Red  Orange  Yellow  Green  Blue  Indigo  Violet ROY G BIV ** Red has the smallest refraction and violet the greatest.

30.  When a laser is shone through a prism, the light will refract but NOT disperse. WHY? A laser light is only one color.

31. Refraction  Refraction: the bending or changing direction of a wave as it passes from one material to another.

32. Spectrum  The range of colors or frequencies of visible light is called the visible Spectrum.

33. Reflection  Reflection: occurs when a light wave strikes an object and bounces off.  When sunlight hits a colored clothing some colors are reflected and others are absorbed.

34. Electromagnetic Radiation  The transmission of energy in the form of waves that extend from the longest radio waves to the shortest gamma waves. http://www.watchknowlearn.org/Video.asp x?VideoID=30186&CategoryID=8281

35. Types of Electromagnetic Radiation  1. Radio Waves: the longest wavelength and lowest energy and frequency.  Can be used to help us see the inside of our bodies to diagnose illness. Ex: MRI Magnetic Resonance Imaging

36. 2. Microwaves: have the shortest wavelength and the highest frequency of all radio waves. Ex: Microwave ovens, telecommunication satellites, radio telescopes, radar (remote sensing). Microwave ovens use a specific frequency that is strongly absorbed by water molecules in food.

37.  3. Infrared Waves: longer wavelength and lower energy and frequency.  Infrared means below red.  Also called heat radiation.  Ex: Remote controls, computer, heat lamps, motion sensors.

38.  4. Visible Light Spectrum : can be continually detected by our eyes.

39.  5. Ultraviolet Waves: shorter wavelength and higher energy and frequency.  Very Energetic  Have the ability to kill bacteria in food and water and medical supplies.  Ex: Sun, detect fingerprints.

41.  6. X-Rays: have a shorter wavelength, and higher energy and frequency than UV.  Used to photograph teeth, bones and the inside of machines, security screening.

42.  7. Gamma Rays: have the highest energy and frequency and the shortest wavelength.  Result from nuclear reactions.  Produced by the hottest regions of the universe. Gamma Rays: Nuclear Explosion Gamma Rays: Medical Treatment

44. Electromagnetic Radiation… A Safety Concern  Generally, higher energy electromagnetic radiation is more harmful to humans.  The Earth`s atmosphere is able to protect us from some of the more dangerous electromagnetic radiation present in space, making the Earth a safe place for humans.  Changes to present conditions may comprise our safety.

45.  https://www.youtube.com/watch?v=jjy- eqWM38g&list=PL8dPuuaLjXtPAJr1ysd5yGIyiSFuh0mIL &index=24 https://www.youtube.com/watch?v=jjy- eqWM38g&list=PL8dPuuaLjXtPAJr1ysd5yGIyiSFuh0mIL &index=24