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The apparent depth of the glass block is less than the real depth.

29.8 Refraction of Light. The apparent depth of the glass block is less than the real depth. The fish appears to be nearer than it actually is. The full glass mug appears to hold more root beer than it actually does.

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The apparent depth of the glass block is less than the real depth.

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  1. 29.8Refraction of Light • The apparent depth of the glass block is less than the real depth. • The fish appears to be nearer than it actually is. • The full glass mug appears to hold more root beer than it actually does. These effects are due to the refraction of light whenever it crosses a boundary between air and another transparent medium.

  2. Light and Sound • In this unit: • Properties of light • Reflection • Colours • Refraction • Properties of sound • Hearing

  3. Light and color

  4. What are some questions you have about light and color? • What is Light? • What causes it?

  5. 5/16 • What are some differences between light and sound? • What is one thing you learned from your classmates yesterday?

  6. Electromagnetic waves Electromagnetic waves – light that travels as a photon through a vacuum or a medium in the form of radio, micro, visible light, or xrays

  7. 27.4Light and Transparent Materials Light is energy carried in an electromagnetic wave, generated by vibrating electric charges. When light strikes matter, electrons in the matter are forced into vibration.

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

  9. Speed of light

  10. 27.2The Speed of Light Light coming from Io takes longer to reach Earth at position D than at position A. The extra distance that the light travels divided by the extra time it takes gives the speed of light. Light year – distance light travels in one year

  11. 27.2The Speed of Light The speed of light in a vacuum is a universal constant. Light is so fast that if a beam of light could travel around Earth, it would make 7.5 trips in one second. Light takes 8 minutes to travel from the sun to Earth and 4 years from the next nearest star, Alpha Centauri. The distance light travels in one year is called a light-year.

  12. polarization

  13. 27.7Polarization If the rope is shaken up and down, a vertically polarized wave is produced. The waves traveling along the rope are confined to a vertical plane. If the rope is shaken from side to side, a horizontally polarized wave is produced.

  14. 27.8Polarized Light and 3-D Viewing A 3-D slide show uses polarizing filters. The left eye sees only polarized light from the left projector; the right eye sees only polarized light from the right projector.

  15. 27.7Polarization A vibrating electron emits a polarized electromagnetic wave. A vertically vibrating electron emits vertically polarized light. A horizontally vibrating electron emits horizontally polarized light.

  16. 27.7Polarization A rope analogy illustrates the effect of crossed sheets of polarizing material.

  17. 27.7Polarization • Light is transmitted when the axes of the polarizing filters are aligned. • Light is absorbed when they are at right angles to each other.

  18. 27.8Polarized Light and 3-D Viewing Try these optical illusions.

  19. 27.8Polarized Light and 3-D Viewing

  20. 27.8Polarized Light and 3-D Viewing

  21. 5/17 • True or false black is a combination of all the colors • What do you see below? • Why is candle light more romantic?

  22. The colors of the objects depend on the color of the light that illuminates them.

  23. Color is in the eye of the beholder and is provoked by the frequencies of light emitted or reflected by things. We see red in a rose when light of certain frequencies reaches our eyes. Many organisms, including people with defective color vision, see no red in a rose.

  24. Color The colors of the objects depend on the color of the light that illuminates them. Color depends on the wavelength that is reflected back.

  25. 28.1The Color Spectrum Isaac Newton was the first to make a systematic study of color. Passing sunlight through a glass prism, Newton showed that sunlight is composed of a mixture of all the colors of the rainbow. Newton called this spread of colors a spectrum, and noted that the colors were formed in the order red, orange, yellow, green, blue, and violet. What is the jist of this passage?

  26. 28.1The Color Spectrum When sunlight passes through a prism, it separates into a spectrum of all the colors of the rainbow.

  27. 28.2Color by Reflection Light Sources • The color of an object depends on the kind of light used. • A candle flame is deficient in higher frequencies; it emits a yellowish light. Things look yellowish in candlelight. • An incandescent lamp emits light of all the visible frequencies, but is richer toward the lower frequencies, enhancing the reds. • A fluorescent lamp is richer in the higher frequencies, so blues are enhanced when illuminated with fluorescent lamps. • Do you think you look better in certain light? • Why is candle light more romantic?

  28. 28.2Color by Reflection • This square reflects all the colors illuminating it. In sunlight, it is white. When illuminated with blue light, it is blue. • This square absorbs all the colors illuminating it. In sunlight it is warmer than the white square.

  29. 28.4Sunlight The radiation curve of sunlight is a graph of brightness versus frequency. Sunlight is brightest in the yellow-green region.

  30. Mini lab: • Which folder will be brighter under red light, blue or red? • Which folder will be brighter under blue light, blue or red? • Expain:

  31. 28.5Mixing Colored Light The low-frequency, middle-frequency, and high-frequency parts of white light appear red, green, and blue. To the human eye, red + green = yellow; red + blue = magenta; green + blue = cyan.

  32. 28.6Complementary Colors Six blocks and their shadows appear as different colors depending on the color of light that illuminates them.

  33. 28.2Color by Reflection Petals of most yellow flowers, such as daffodils, reflect red and green as well as yellow. Yellow daffodils reflect light of a broad band of frequencies. The reflected colors of most objects are not pure single-frequency colors, but a spread of frequencies. So something yellow, for example, may simply be a mixture of colors without blue and violet—or it can be red and green together. Main idea : The color you see is a combination of frequencys that are reflected back into your eye.

  34. Why is the sky blue

  35. Why is the sky blue? • Sunlight reaches Earth's atmosphere and is scattered in all directions by all the gases and particles in the air. Blue light is scattered in all directions by the tiny molecules of air in Earth's atmosphere. Blue is scattered more than other colors because it travels as shorter, smaller waves. This is why we see a blue sky most of the time.

  36. What Makes a Red Sunset?

  37. 28.8Why the Sky Is Blue The sky is blue because its component particles scatter high-frequency light.

  38. 28.8Why the Sky Is Blue or black The higher that one goes into the atmosphere, the fewer molecules there are in the air to scatter light. The sky appears darker. When there are no molecules, as on the moon, for example, the “sky” is black.

  39. Law of reflection The angle of incidence = the angle of reflection

  40. Refraction – the bending of light due to bending of light Coming up next on Monday snell’s law

  41. Which topic did you choose? • What is the main idea behind your topic? • Today – • -present your findings to classmate • -Fill out exit slip

  42. 5/15 • Are you ready to present? • What are some characteristics of a strong presentation? • Exit slip – write a paragraph reflection on how you did. What was the main idea. What extra information did you have. Rate yourself 1-5. What did you do well, what could use work?

  43. 5/16 • 1. What is one thing you learned from your classmates regarding light?

  44. Light travels much faster than sound. For example: • Thunder and lightning start at the same time, but we will see the lightning first. • 2) When a starting pistol is fired we see the smoke first and then hear the bang.

  45. Properties of Light summary • Light travels in straight lines • Light travels much faster than sound • We see things because they reflect light into our eyes • Shadows are formed when light is blocked by an object

  46. We see things because they reflect light into our eyes: Homework

  47. 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

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