Electromagnetic Waves & the Electromagnetic Spectrum

1. Electromagnetic Waves &the Electromagnetic Spectrum • Students will ask questions and define problems to show understanding of electromagnetic waves highlighting the relationship between energy and matter.

2. Electromagnetic Waves • Transverse waves without a medium! • (They can travel through empty space)

3. They travel as vibrations in electrical and magnetic fields. • Have some magnetic and some electrical properties to them.

4. When an electric field changes, so does the magnetic field. The changing magnetic field causes the electric field to change. When one field vibrates—so does the other. • RESULT-An electromagnetic wave.

5. Electromagnetic radiation • The energy that electromagnetic waves transfer through matter or space

6. Electromagnetic waves travel VERY FAST – around 300,000 kilometres per second (the speed of light). • At this speed they can go around the world 8 times in one second.

7. Electromagnetic Waves. • What are the two models that explain how Electromagnetic Waves Behave. • Wave Model of light • Particle Model of Light

8. Wave Model of Light • The wave model of light pictures light travelling as a wave. It doesn't explain everything about how light behaves but it helps us visualize it. Thinking about light travelling in waves helps to explain unpredictable behavior, like when light curves around a opening. • https://www.youtube.com/results?search_query=electromagnetic+waves+crash+course+

9. Polarized light • When light passes through a polarized filter, it has the properties of the wave. An ordinary beam of light consist of waves that vibrate in all directions. A polarized filter act as though it has tiny slits aligned in only one direction. When light enter a polarizing filter, only some of the waves pass trough. The light that passes through is called polarized light.

10. Polarized light

11. Polarized light

12. Polarized light • https://www.youtube.com/watch?v=QO-QjSMTYr4

13. Waves or Particles? • Electromagnetic radiation has properties of waves but also can be thought of as a stream of particles. This is called the Photoelectric Effect • Example: Light • Light as a wave: Light behaves as a transverse wave which we can filter using polarized lenses. • Light as particles (photons): When directed at a substance light can knock electrons off of a substance (Photoelectric effect)

14. Particle Model of Light • Light is made up of little tiny particles called photons. • https://prezi.com/ubspgiw4cjrd/particle-model-of-light/

15. Photoelectric Effect • Photons are also know as packets of light energy

16. Photoelectric Effectphotons hitting a metal surface knock out the electrons.

17. Photoelectric Effect • https://www.youtube.com/watch?v=7wF8Jm5Zhvk

18. Let’s review • A _____________ is a tiny packet of energy. • What does a polarizing filter do? • What are the two models that explain how light behaves?

19. Let’s review • A _Photons____ is a tiny packet of energy. • What does a polarizing filter do? • What are the two models that explain how light behaves?

20. Let’s review • A _Photons____ is a tiny packet of energy. • What does a polarizing filter do? A POLARIZINFG FILTER ONLY LETS WAVES THROUGH THAT ARE VIBRATING IN A CERTAIN DIRECTION. • What are the two models that explain how light behaves?

21. Let’s review • A _PHOTONS____ is a tiny packet of energy. • What does a polarizing filter do? A POLARIZING FILTER ONLY LETS WAVES THROUGH THAT ARE VIBRATING IN A CERTAIN DIRECTION. • What are the two models that explain how light behaves? THE WAVE MODEL OF LIGHT AND THE PARTICLE MODEL OF LIGHT

22. Electromagnetic Spectrum—name for the range of electromagnetic waves when placed in order of increasing frequency • GAMMA RAYS • ULTRAVIOLET RAYS • RADIO WAVES • INFRARED RAYS • X-RAYS • MICROWAVES • VISIBLE LIGHT

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

25. RADIO WAVES • Have the longest wavelengths and lowestfrequencies of all the electromagnetic waves.

26. Global Positioning Systems (GPS) measure the time it takes a radio wave to travel from several satellites to the receiver, determining the distance to each satellite.

27. A radio picks up radio waves through an antenna and converts it to sound waves. • Each radio station in an area broadcasts at a different frequency. • # on radio dial tells frequency.

28. MRI • (MAGNETIC RESONACE IMAGING) Uses Short wave radio waves with a magnet to create an image.

29. MICROWAVES • Have the shortest wavelengths and the highest frequency of the radio waves.

30. Used in microwave ovens. • Waves transfer energy to the water in the food causing them to vibrate which in turn transfers energy in the form of heat to the food.

31. RADAR (Radio Detection and Ranging) • Used to find the speed of an object by sending out radio waves and measuring the time it takes them to return.

32. INFRARED RAYS • Infrared= below red • Shorter wavelength and higher frequency than microwaves.

33. You can feel the longest ones as warmth on your skinWarm objects give off more heat energy than cool objects.

34. Therefore people give off infrared rays. Heat lamps give off infrared waves. • Thermogram—a picture that shows regions of different temperatures in the body. Temperatures are calculated by the amount of infrared radiation given off.

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

36. 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 ROYGBIV.

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

38. Used to kill bacteria. (Sterilization of equipment)

39. Too much can cause skin cancer. • Use sun block to protect against (UV rays)

40. Causes your skin to produce vitamin D (good for teeth and bones)

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

42. Bones and teethabsorb x-rays. (The light part of an x-ray image indicates a place where the x-ray was absorbed)

43. Too much exposure can cause cancer (lead vest at dentist protects organs from unnecessary exposure)

44. Used by engineers to check for tiny cracks in structures. • The rays pass through the cracks and the cracks appear dark on film.

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

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

47. The Incredible Hulk was the victim of gamma radiation.

48. Exploding nuclear weapons emit gamma rays.

49. Brief SUMMARY • A.All electromagnetic waves travel at the same speed. (300,000,000 meters/second) 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.