Pick up Light Packet & Light WS

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Bryce Ford
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1 Pick up Light Packet & Light WS Only sit or stand at a station with a cup. Test or Quiz Make Ups Today/Tomorrow after School Only. Sound Test Corrections/Retakes: Wednesday, Next Tuesday, Wednesday, Thursday After School Only

2 Light Notes Student Stations

3 What can you see?

4 What can you see? The only thing you see is LIGHT! This unit is self guided up to Mirror Diagrams and Mirror Calculations This week you will collect the information from all the slides in this presentation in station form. Complete Light WS Complete Light Quiz This should all be done by Thursday end of class

5 Light is a form of energy. Light travels in a straight line Light speed is 3.0 x 10 8 m/s Light is carried by photons Light can travel through a vacuum Light is a transverse wave Light is an electromagnetic wave (EM)

6 All electromagnetic waves are transverse waves. They have electric and magnetic components which vibrate perpendicular to each other.

14 dual nature of light Is light a particle or a wave

15 Example 1: A beam of light has a wavelength 1 x 10-3 m. What is its speed? Is it an X Ray? Why or why not?

16 "Courtesy of the Advanced Light Source, Berkeley Lab."

17 Example 2: The wavelength of an electromagnetic wave measures 3.63 x 10-9 m. What is the frequency of this waveform? Is it an infrared wave? Why or Why not? Given: Formula: Substitution Answer and Units

18 "Courtesy of the Advanced Light Source, Berkeley Lab."

19 Example 3: An EM wave has a frequency of 1 x Hz. What is its wavelength? What type of wave is it? Is it high or low energy? Given: Formula: Substitution Answer and Units

20 "Courtesy of the Advanced Light Source, Berkeley Lab."

21 Tour of EM Spectrum

22 What you need to know about the EM Spectrum Order of the different portions according to wavelength, frequency, and energy. You do not need to memorize numbers! Examples of each portion

23 740nm 370nm

24 Wavelength: 1m to m Frequency: 3 x 10 9 to 3 x 10 4 Hz Uses: Telecommunications, TV, Radio Dangers: none

25 Wavelength: 0.001m to 1m Frequency: 3 x to 3 x 10 9 Hz Uses: Telecommunications, RADAR, Cooking Dangers: can produce burns, cataracts, cancer (?)

26 Wavelength: 740nm to 0.01m Frequency: 4 x to 3 x Hz Uses: Heating, cooking, TV remotes, night-vision Dangers: can burn

27 Wavelength: 370nm (violet) to 740nm (red) Frequency: 8 x to 4 x Hz Uses: seeing Dangers: eye damage from bright lights Visible light is best at getting through our atmosphere which is why we use it to see!

28 Visible Spectrum Low Freq, Long λ High Freq, Short λ

30 Wavelength: 10-9 m to 370nm Frequency: 3 x to 8 x Hz Uses: discos, tanning salons, counterfeit detections, pollination Dangers: skin cancer Bees see in UV to help them find pollen!

Wavelength: 10-12 to 10-7 m Frequency: 3 x 10 20 to 3

31 Wavelength: to 10-7 m Frequency: 3 x to 3 x Hz Uses: medical imagery, security Dangers: cancer Hand with Rings by Wilhelm Röntgen. The first "medical" X-ray of his wife's hand taken on 22 December 1895.

32 Wavelength: to 10-9 m Frequency: 3 x to 3 x Hz Uses: cancer treatment, observing the universe Dangers: cancer ( )

33 Memorization Trick Red Low Radio High Gamma Vi

34 "Courtesy of the Advanced Light Source, Berkeley Lab."

35 Refer to the chart of the EM Spectrum answer the following: As wavelength increases, frequency and energy As frequency increases, wavelength and energy Longest EM Wave Shortest EM Wave Longest Visible Light Color Shortest Visible Light Color

36 The Dangers of the EM Spectrum As the wavelength of EM spectrum changes, the way the different wavelengths interact with matter also changes. As the frequency increases, wavelength gets smaller. Eventually the waves are so small that they can interact with cells, DNA and atoms. This is called IONISING RADIATION. NON-IONISING IONISING

37 How we see Color and Intensity sensitive cells on retina image inverted due to refraction by lens. Signal sent to brain via optic nerve

38 What we see: In visible spectrum nm If you see red, object absorbs all frequencies of visible light but red, ie object reflects red White: combination of all visible light frequencies, all frequencies reflected Black: combination of all visible light frequencies absorbed, no frequencies reflected

39 Rod Cells: sensitive to brightness Obeys inverse square law Brightness is inversely related to the square of the distance from the source

40 Cone cells: detect color Detect the 3 primary colors of light: red, blue, and green (not to be confused with the primary colors of pigment (red, blue and yellow) you learned in elementary school.)

41 Colors of Light Primary Blue Red Green Secondary B + R = Magenta B + G = Cyan R + G = Yellow

42 Can you get sunburnt sitting inside your car with windows up? Record this information in margin by Terms You should Know 42

43 Ultraviolet light (particularly UVB) oscillates at too high a frequency for electrons in glass molecules, while infrared is too low. Visible light is just right. Making glass transparent to visible light and opaque to some infrared and some ultraviolet. Yes you can get sumburnt through some types of glass!

44 Reflection and Refraction at an Interface Why does the light bend?

45 When Light approaches a Boundary it can: Be Absorbed ( Stuck inside ) Pass through the boundary (transmitted) Medium Changes Therefore Speed Changes What is this called? Refraction Bounce off the boundary Medium its traveling through does not change Therefore Speed remains same What is this called? Reflection Any Combination of the above! 45

46 Law of Reflection

47 Try This!

48 If all surfaces reflect, why can t I see my image?

49 Light reflection from a smooth surface is called regular or specular reflection. Light reflection from a rough or irregular surface is called diffuse reflection.

51 What type of reflection?

52 TOTAL INTERNAL REFLECTION Light gets trapped in a dense medium and continuously reflects in that medium. This is the basis of Fiber Optics!

54 Record this information about the sky and the sun by the rainbow

57 Polarized Sunglasses- How do they work? light waves vibrate in more than one plane light waves can be made to vibrate in a single plane by use of polarizing filters. 57

59 Object: source of rays Image: reproduction of object When we look at something in the mirror, the light wave we see is the reflected ray

60 3 Ways to Describe Images 1. Size Same Reduced Enlarged 2. Orientation Upright or inverted, Reversed 3. Virtual or Real 60

61 Virtual Images reflected rays do not actually converge to form image. Cannot be projected. images form where light rays appear to have crossed. In mirrors, they form behind the mirror. are always upright. 61

62 Real Images images form where light rays actually cross. Can be projected. In mirrors, they form on the same side of the mirror as the object since light can not pass through a mirror. are always inverted (flipped upside down). Objects that your see are projected onto your on your retina. They are inverted! They are real images. 62

63 The following three slides refer to the large mirrors and a demo that I have in the classroom. We will go over this information again in class next week.

64 Convex Mirror or Diverging Mirror Look at your image close up Are you Upright or Inverted? Is that a real or virtual image? What about your size? Now, move away from the mirror and see what happens. What changed?

65 Concave Mirror or Converging Mirror Look at your image close up Are you Upright or Inverted? Is that a real or virtual image? What about your size? Now, move away from the mirror and see what happens. What changed?

66 The secret of the floating pig is due to 2 curved mirrors that form a Real Image!!

67 Can you answer the following?

68 EM Station Fast Check Name: 1. Why are EM Waves called EM Waves? 2. Are EM Waves mechanical or non-mechanical? 3. Are EM Waves transverse or longitudinal? 4. What is a photon? 5. Is light a particle or a wave? Period: 6. What is common between a radio wave, the color purple, and an X ray? 7. What is the difference between a radio wave, the color purple, and an X ray?

69 CHECK YOUR ANSWERS!!!!

70 Example 1: A beam of light has a wavelength 1 x 10-3 m. What is its speed? Is it an X Ray? Why or why not? Given: Formula: Substitution Answer and Units λ = 1 x 10-3 m c = 3.00 x 10 8 m/s c = fλ Not needed. All EM waves travel at 3.00 x 10 8 m/s! Not needed. All EM waves travel at 3.00 x 10 8 m/s! Microwave If you check the chart you will notice that microwaves have a length in 1 x 10-3 m range

71 Example 2: The wavelength of an electromagnetic wave measures 3.63 x 10-9 m. What is the frequency of this waveform? Is it an infrared wave? Why or Why not? Given: λ = 3.63 x 10-9 m c = 3.00 x 10 8 m/s Formula: c = fλ f = c/λ Substitution f = (3.00 x 10 8 m/s) / (3.63 x 10-9 m) Answer and Units f = 8.26 x Hz UV If you check the chart you will notice that UV light has a frequency in Hz range

72 Example 3: An EM wave has a frequency of 1 x Hz. What is its wavelength? What type of wave is it? Is it high or low energy? Given: f = 1 x Hz c = 3.00 x 10 8 m/s Formula: c = fλ λ = c/f Substitution λ = (3.00 x 10 8 m/s) / (1 x Hz ) Answer and Units 3.00 x m Gamma ray. Highest Energy. Refer to chart

73 Refer to the chart of the EM Spectrum answer the following: As wavelength increases, frequency decreases and energy decreases As frequency increases, wavelength decreases and energy increases Longest EM Wave radio Shortest EM Wave gamma ray Longest Visible Light Color red Shortest Visible Light Color violet

74 Did you get 65? Ex 4

75 Why are EM Waves called EM Waves? They are composed of an electrical wave and a magnetic wave that vibrate perpendicular to one another Are EM Waves mechanical or non-mechanical? non-mechanical no medium needed can travel in vacuum of space Are EM Waves transverse or longitudinal? transverse What is a photon? packet of light energy Is light a particle or a wave? Both: dual nature of light What is common between a radio wave, the color purple, and an X ray? All travel at same speed C! 3 x 10 8 m/s What is the difference between a radio wave, the color purple, and an X ray? They vary by frequency and wavelength c = fʎ is just v = fʎ

76 Links to video for fun!

77 Eye anatomy Biologix: The eye Vision and Perception (29min)

78 Primary colors of light primary colors of light (3:48min) k

79 What are the primary colors of light? How do you see color How do we see color 402 What color is the dress How colorblind people see the world Color Demo PPT 79

80 Light and Color Nye (4:48min) What makes up white light? How do we see individual colors? What are we seeing when we look at something white? What are we seeing when we look at something black? Why do we wear white in the summer?

81 Light and Color Nye What makes up white light? All the colors How do we see individual colors? We see the unabsorbed or reflected color What are we seeing when we look at something white? All colors reflected What are we seeing when we look at something black? All colors absorbed, energy converted to heat Why do we wear white in the summer? Since all colors reflected, energy reflected (less heat)

All forms of EM waves travel at the speed of light in a vacuum = 3.00 x 10 8 m/s This speed is constant in air as well

All forms of EM waves travel at the speed of light in a vacuum = 3.00 x 10 8 m/s This speed is constant in air as well Pre AP Physics Light & Optics Chapters 14-16 Light is an electromagnetic wave Electromagnetic waves: Oscillating electric and magnetic fields that are perpendicular to the direction the wave moves Difference