1. Electromagnetic Waves (light) & the Electromagnetic Spectrum

2. Waves All waves carry … ENERGY!!!

3. Electromagnetic Waves (light) Light waves are transverse waves

4. Electromagnetic Radiation  Energy emitted from the sun that travels to earth through space.  They contain electrical and magnetic properties.  Have some magnetic and some electrical properties to them.

5. 1.Split into groups 6 2.Make each of the following medium with the members of your group  Solids – particles close together (shoulder to shoulder)  Liquids – particles spread out a little (hands on hips apart)  Gas – particles spread far apart (arms out apart)  Vacuum – no particles (no students ) 3. One member of the group (light) has to travel between each member of the group. 4. Which medium is light the fastest? 5. Which medium is light the slowest? EM(electromagnetic)Wave Speed

6.  EM waves travel fastest when there is no matter (particles) in the way.  Does not need a medium to travel ex: light can travel trough space  Speed depends on the medium slowest fastest medium vacuum (solid – liquid - gas) (space)

7.  Electromagnetic waves travel VERY FAST – around 300,000 km/s (the speed of light). At this speed they can go around the world 8 times in one second!!!

8.  Electromagnetic Spectrum—name for the range of electromagnetic waves when placed in order of increasing frequency (decreasing wavelength) RADIO WAVES MICROWAVES INFRARED RAYS VISIBLE LIGHT ULTRAVIOLET RAYS X-RAYS GAMMA RAYS

9. Notice the wavelength is long (Radio waves) and gets shorter (Gamma Rays)

11. RADIO WAVES  Have the longest wavelengths and lowest frequencies of all the electromagnetic waves.

12.  Global Positioning Systems (GPS)

13.  Radio  MRI (MAGNETIC RESONACE IMAGING)

14. MICROWAVES Have the shorter wavelengths and the higher frequency than radio waves.

15. Microwave ovens. Cell Phones

16. INFRARED RAYS  Infrared (below red)  Shorter wavelength and higher frequency than microwaves.

17. Infrared Waves You can feel these as warmth on your skin Warm objects give off more heat energy than cool objects.

18. Thermogram  People give off infrared rays. Heat lamps.

19. VISIBLE LIGHT Electromagnetic waves we can see. Shorter wavelength and higher frequency than infrared rays. Longest wavelength= red light Shortest wavelength= violet (purple) light

20. When light enters a new medium it bends (refracts). Each wavelength bends a different amount allowing white light to separate into it’s various colors ROYGBV.

21. ULTRAVIOLET RAYS Shorter wavelength and higher frequency than visible light Carry more energy than visible light

22. UV Rays Used to kill bacteria. (Sterilization of equipment) Used in tanning beds – VERY DANGEROUS

23. UV Rays – good & bad Bad: Too much can cause skin cancer. Use sun block to protect against (UV rays) Good: Causes your skin to produce vitamin D (good for teeth and bones)

24. X- RAYS  Shorter wavelength and higher frequency than UV-rays  Carry a great amount of energy  Can penetrate most matter.

25. X-Rays: Doctors & Dentists use Bones and teeth absorb x-rays Used by engineers to check for tiny cracks in structures.

26. Too much exposure can cause cancer (lead vest at dentist protects organs from unnecessary exposure) Too Much Is Dangerous!!!

27. GAMMA RAYS  Shorter wavelength and higher frequency than X-rays  Carry the greatest amount of energy and penetrate the most.

28. Used in radiation treatment to kill cancer cells. Can be very harmful if not used correctly.

29. Exploding nuclear weapons emit gamma rays.

30.  Brief SUMMARY  A. All electromagnetic waves travel at the same speed. (300,000,000 m/s) in a vacuum.  B. They all have different wavelengths and different frequencies.  Long wavelength-  lowest frequency  Short wavelength  highest frequency  The higher the frequency the higher the energy.

31. More Examples  http://www.darvill.clara.net/emag/emaginfra.htm http://www.darvill.clara.net/emag/emaginfra.htm

33. SPS9c: Compare and contrast the characteristics of electromagnetic and mechanical (sound) waves. SPS9e: Relate the speed of sound to different mediums.

34. Sound Waves (compressional)  Sound waves are longitudinal waves  Also called mechanical waves because vibrations MOVE from particle to particle.

35. 1.Split into groups 2.Make each of the following medium with the members of your group  Solids – particles close together (shoulder to shoulder)  Liquids – particles spread out a little (hands on hips apart)  Gas – particles spread far apart (arms out apart)  Vacuum – no particles (no students ) 3. A ball will be passed from hand to hand as quickly as possible. 4. Which medium is light the fastest? 5. Which medium is light the slowest? Sound Wave Speed

36. Sound Waves  Sound travels faster when the particles in a substance are closer together – MUST HAVE PARTICLES TO MOVE! slowest fastest Gas Liquid Solid  Wave speed of sound depends on the medium  Sound does not travel through a vacuum (no matter/particles) ex: space

37.  https://www.youtube.com/watch?v=figQeyS p7Ec https://www.youtube.com/watch?v=figQeyS p7Ec

38. Sound Waves  Mechanical (sound) waves MUST have a medium to travel through.  No medium – no sound  What is wrong with this video? http://www.youtube.com/watch?v=qniy8aDSFLA&safety_mode =true&persist_safety_mode=1

39. Sound waves CANNOT travel through space!!!!!!!

40. Sound Waves vs. Light Waves  Light moves faster than sound in thunderstorms!!!  Ex: Lighting and thunder occur at the same time but you see lighting before you hear thunder because light travels faster than sound through a gas  https://www.youtube.com/watch?v=Jm3rHO NOr9o https://www.youtube.com/watch?v=Jm3rHO NOr9o

41. Speed = wavelength x frequency v = × f v f

42. D. Measuring Waves  Velocity ( v )  SPEED of a wave as it moves forward  depends on wave type and MEDIUM v = × f v:velocity (m/s) :wavelength (m) f:frequency (Hz)

43. WORK: v = × f v = (3.2 m)(0.60 Hz) v = 1.92 m/s D. Measuring Waves  EX: Find the velocity of a wave in a wave pool if its wavelength is 3.2 m and its frequency is 0.60 Hz. GIVEN: v = ? = 3.2 m f = 0.60 Hz v f

44. WORK: f = v ÷ f = (5000 m/s) ÷ (417 m) f = 12 Hz D. Measuring Waves  EX: An earthquake produces a wave that has a wavelength of 417 m and travels at 5000 m/s. What is its frequency? GIVEN: = 417 m v = 5000 m/s f = ? v f

45. Your Turn  An earthquake produces a wave that has a wavelength of 210 m and travels at 7000 m/s. What is its frequency?  Find the velocity of a wave in a wave pool if its wavelength is 6 m and its frequency is 0.90 Hz.

47. Doppler Effect  An observed change in the frequency of a wave when the source or observer is moving.  The pitch of a sound, high or low, depends on the frequency of sound waves.  Frequency changes when the source is moving.  https://www.youtube.com/watch?v=Djz_rtnXSfY https://www.youtube.com/watch?v=Djz_rtnXSfY  example example

48. Doppler Effect If a sound source is moving towards you – it has a high pitch. If a sound source moves away from you – it has a low pitch.

49. Reflection  Reflection is the bouncing back of a wave as it meets a surface or a boundary.

50. Diffraction  The bending of waves as they pass an edge or opening.

51. Refraction  Refraction is the bending of waves as they pass from one medium into another.

52. Interference  Interference is the combination of two or more waves that exist in the same place at the same time.  Constructive interference always results in a new wave that is bigger than the original waves.  Destructive interference always results in a new wave that is smaller than the largest of the original waves.  Examples Examples