Light

1. Light

2. The EKG showed that • Sound is another form of electricity • Your body has currents moving through it • We emit strong magnetic fields • The device charges up your body periodically

3. The speaker/microphone helped us to see that: • Electrical currents can be produced from a moving magnet • Sound is really a form of electricity • There is no magnetism involved in the conversion from sound to electrical current • Sound waves can only be emitted from electrical activity, not the other way around

4. Light travels VERY FAST – around 300,000 kilometres (186282 miles) per second. At this speed it can go around the world 8 times in one second.

5. HIGH energy LOW energy

6. The Full Electromagnetic Spectrum • Visible, Infrared and UV radiation are only part of the full spectrum of electromagnetic radiation Source: http://www.mhhe.com/physsci/astronomy/arny/instructor/graphics/ch03/0305.html

7. The Sun’s Radiation Spectrum • ~ 43% is in the visible range • ~ 49% is in the near infrared range • ~ 7% is in the ultraviolet range • < 1% is x-rays, gamma waves, and radio waves Most of the sun’s radiation is UV, Vis & IR : . Source: Adapted from http://www.ucar.edu/learn/imgcat.htm

10. Sunset

11. By passing white light through a prism, • you can tell- • A that white light is actually a mixture of different colors • B the mass of the prism • C the original source of the light • D that blue light is brighter than white • light

12. Pick up nov 4

13. Did you vote? • Yes! • No… • I am not able to vote

14. Do you think that your vote “counts?” • Yes, definitely • Only indirectly • Only if it is a close call • No

15. November exam Exam this month – push back a week? • 10-Nov is ok • Prefer 17-Nov • No exam at all is preferable Final: Wed Dec 15, 4:30-7pm (I think this room)

16. Do you want to go over the “nuclear” exam in Thursday discussion session? • Yes • No • Indifferent

17. What about for the circuits hw? • Yes • No • Indifferent

18. Bees see in UV

38. Additive Colors • Red, Green, and Blue light sources can be used to synthesize almost any perceivable color • Red+ Green = Yellow • Red + Blue = Magenta • Green + Blue = Cyan • These three dual-source colors become the primary colors for subtraction • why? because absence of green is magenta • absence of red is cyan, etc.

39. Pick up Nov 9

40. Term project – to be worth more? Do you find it fair to change the grading scheme for this course based on a class vote? • Yes, if >50% is ok with it. • Yes, but only if >67% is ok with it. • Not really, but I’ll go along with it. • No way!

41. Term project – to be worth more? There are multiple ways to slice it – • Midterms=13%,final=20%, term=18% • Midterms=13%,term=15% • Midterms same, final 20%, term 14% • Keep the current scheme

42. Democracy! Are you ok with what “we” just decided? • Yes • No

43. Invisibility cloak?

44. One-way mirrors How do they work? • Special engineered one-way material • Bright reflected rays on one side • Interference of light rays • Refraction of light rays

45. Part 2 - Reflection Reflection from a mirror: Normal Reflected ray Incident ray Angle of reflection Angle of incidence Mirror

46. A “light-pipe” works by • Diffraction • Interference • Refraction • Dispersion

49. Homework Seeing colour • The colour an object appears depends on the colours of light it reflects. For example, a red book only reflects red light: White light Only red light is reflected

50. pick up Nov 11