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REFRACTION

REFRACTION. Chapter 11.1. Japanese Scientist Cloaking Device https ://www.youtube.com/watch?v= PD83dqSfC0Y Philadelphia Experiment : http://www.youtube.com/watch?v= 8BtJx33ea0o Invisible Cloak for Tanks: http://www.youtube.com/watch?v=KL_KdmSTSNA&feature= related

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REFRACTION

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  1. REFRACTION Chapter 11.1

  2. Japanese Scientist Cloaking Devicehttps://www.youtube.com/watch?v=PD83dqSfC0Y Philadelphia Experiment: http://www.youtube.com/watch?v=8BtJx33ea0o Invisible Cloak for Tanks: http://www.youtube.com/watch?v=KL_KdmSTSNA&feature=related How does cloaking work? http://www.howstuffworks.com/invisibility-cloak.htm

  3. What is Refraction??? Refraction is the bending of light as it travels from one medium into another. Refraction of Light in Glass: http://www.teachersdomain.org/asset/lsps07_int_refractdemo/

  4. Refraction in a Prism Density Change R O Y G B I V Dispersion: process of separating colours by refraction Density Change Medium: air  glass air

  5. Can you identify the media?

  6. …Refraction… • Light travels in a straight line and at a constantspeed when travelling in the SAME medium • Speed of light in a vacuum is 3.0x108 m/s but as light enters another medium, it slows down. • the particles of the medium prevent the light waves from traveling

  7. Refraction air water

  8. What causes light to refract? Refraction can be compared to the behaviour of a car, if two wheels were on the shoulder and two on the road.

  9. What causes light to refract? This edge slows first in the grass This edge slows first in the glass

  10. Learning Check TB: Pg.451 # 1 - 4

  11. RECALL: Light travels in a straight line and at a constant speed when travelling in the SAMEmediumbut…

  12. When Light enter a lessdense substance it will bend away from the NORMAL Less dense more dense

  13. When light enters a moredense substance it will bend towardsthe NORMAL less dense more dense

  14. LIGHT & the Normal Light entering another transparent medium @ 90° will not bend, So no refraction will occur Some light is reflected and the rest travels through, although it will change speed!

  15. REFRACTION: Step by Step Substance B Which is more dense? A or B Substance A This edge speeds up first in Substance A

  16. REFRACTION: Step by Step Substance B Which is more dense? A or B Substance A This edge slows down first in the denser substance

  17. Which is more dense?

  18. Refraction Using Rays Pg. 451

  19. Refraction Using Rays normal Reflected ray Incident ray Ѳr Ѳi Air Water ѲR Refracted ray

  20. An extra ray...Do you see it??? Angle of refraction: is the anglebetween the refracted ray and the normal.

  21. Effects & Consequences of Refraction Why do the objects appear in a different direction? http://www.dnatube.com/video/11605/Refraction-Of-Light

  22. Why do objects appear different in water? Medium = air Apparent object Medium = water Actual object

  23. The Refraction of Light Refraction can make objects immersed in water appear broken, and can create mirages.

  24. POLE in a POOL

  25. POOLS are Dangerous Water in a pool will bend light making the pool seem more shallow than it really is. The APPARENT Depth is what we see, it is shallower than the ACTUAL Depth. One way to minimize this difference in depth is to look directly down into the water. Dogs know this??? They will start to doggy paddle over any depth of water, before you place them in it!

  26. Refraction: Consequences LENS in the EYE CORNEA & EYE LENS bends light to focus it on the RETINA EYE LENS is a flexible lens that can be stretched by the attached muscles.

  27. Index of Refraction Invisible Glass: http://www.youtube.com/watch?v=KyWgnFm3ebc

  28. Index of Refraction Index of refraction (n) = ratioof the speed of light in a vacuum (c) to the speed of light in a given material (v) The index n varies slightly with the colour of light except in a vacuum. This is because different colours of light have different wavelengths The term “optically dense” is used when referring to a medium in which the speed of light decreases.

  29. Index of refraction Speed of light (m/s) Index of refraction (no units) Speed of light in a different material (m/s)

  30. Example 1 • Calculate the index of refraction of a diamond, if the speed of light in a diamond is 1.24 x 108 m/s? • Given: • Unknown: • Equation: • Substitute • Solve: • State:

  31. Solution 1 • Given: • c = 3.00 x 108 m/s • v = 1.24 x 108 m/s • Unknown: n = ? • Equation: n = c / v • Solve: n = 3.00 x 108 m/s / 1.24 x 108 m/s = 2.42 • State: The index of refraction of a diamond is 2.42.

  32. Example 2 • s • Calculate the speed of light in zircon using the index of refraction and express the speed in terms of c, the speed of light. • Given: • Unknown: • Equation: • Solve: • State:

  33. Solution 2 • Given: • c = 3.00 x 108 m/s • n = 1.92 • Unknown: v = ? • Equation: n = c / v v = c / n • Solve: v = 3.00 x 108 m/s / 1.92 = 1.56 x 108 m/s • State: The speed of light in zircon is 1.56 x 108 m/s

  34. Workity work work… TB: Pg. 455 #1 – 4 TB: Pg. 456 # 1 – 8 WS: Index of Refraction

  35. Snell’s Law Not in curriculum???

  36. The Refraction of Light The angle of refraction is related to the different speeds: The speed of light in a medium is given by the index of refraction of that medium:

  37. The Refraction of Light We can now write the angle of refraction in terms of the index of refraction:

  38. The Refraction of Light If light enters a medium of lower index of refraction, it will be bent away from the normal. If the angle of incidence is large enough, the angle of refraction is 90°; at larger incident angles the light will be totally reflected.

  39. The Refraction of Light This is called total internal reflection, and the incident angle at which the angle of refraction is 90° is called the critical angle, C. Total internal reflection is used in some binoculars and in optical fibers.

  40. The Refraction of Light There is a special angle called Brewster’s angle; light reflected at this angle is totally polarized. Reflected light is completely polarized when the reflected and refracted beams are at right angles to one another. The direction of polarization is parallel to the reflecting surface.

  41. The Refraction of Light Brewster’s angle can be calculated using the appropriate geometry:

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