1. Chapter 18: Light and Optics

2. Objectives Summarize the science of optics. Describe how mirrors and lenses can be combined to make complex optical tools. Explain how optical tools are used to extend natural vision. Recognize how laser light is made and used in optical technology

3. Optics is the science of light and vision Optics is the study of visible light and the ways in which visible light interacts with the eye to produce vision. Mirrors, lenses, eyeglasses, cameras, lasers are all optical tools.

4. Fiber Optics Used to transmit information efficiently. EX) Fiber Optic Cables.

5. Fiber Optics Is Technology based on the use of light to send signals through transparent wires called optical fibers Very important in communications for telephones, TV wires, and broadband internet connections. Medical uses to see inside a patients body

6. Lasers A laser is a device that produces an intense, concentrated beam of light that is brighter than sunlight. A laser is made in a special tube called an optical cavity in which an energy source stimulates material to give off light waves.

7. Laser Beams A Laser Beam can travel great distances without spreading because its light waves are parallel and very concentrated. The light waves in a laser beam are all one wavelength and in one phase.

8. Uses of Lasers Surveyors use them to measure distances and angles. Used to read bar codes, to scan images and pages of text and to create holograms

9. Future Uses of Lasers Scientist plan to use them in nanotechnology— perform extremely fine operations. New ways of transferring energy. Supply energy for the spacecraft.

10. Mirrors and Lenses can be more Powerful Optical Tools For example: Mirrors and lenses can be combined with each other, as they are in an overhead projector.

11. Microscopes Used to see small objects. A Microscope enlarges images using a combination of convex lens. (2) Most microscopes use a light or mirror to shine more light on the object. Page 613

12. Telescopes A reflection telescope has a CONCAVE mirror that gathers and focuses light.

13. Telescopes Used to see objects to far away to see well with the naked eye. 2 Types: Refracting telescope is made by combining lenses. Reflection is made by combining lenses and mirrors.

14. Refraction Reflection

15. Lights, Camera, Action…………. Most film cameras focus images Like the eyes Read Page 614

16. Objectives Describe how mirrors control reflection. Describe how mirrors produce images. Identify how a material medium can refract light. Describe how lenses control refraction. Recognize how lenses produce images.

17. Mirrors use Regular Reflection When light waves strike an object, they either pass through it or they bounce off its surface. The law of reflection states that the angle of reflection equals the angle of incidence.

18. Regular Reflection The reflection of parallel light rays all in the same direction is called regular reflection. Surface of the object is smooth, like a mirror, light rays that come from the same direction will bounce off in the same new direction.

19. Diffuse Reflection If the surface is not very smooth, light rays strike it from the same direction and bounce off in many new directions. The reflection of parallel light rays in many different directions is called diffuse reflection. EX) Paper, Cloth

20. An Image When you look in the mirror, you see an image of yourself. An image is a picture of an object formed by waves of light. The image of yourself is reflected off of you, onto the mirror.

21. Law of Reflection States that the angle of incidence equals the angle of reflection EX) A ray of light hits a mirror at an angle of incidence, the reflection angle is equal.

22. Focal Length The focal length of a lens is the distance from the center of a lens to its focal point.

23. Flat Mirrors Looks Exactly like you Produces an image that is identical, but opposite to how you look

24. Convex A Convex mirror or lens is curved outward.  A convex lens brings light rays to a focal point. The distance from the center of the lens to the focal point is the focal length.  A convex lens forms a “right-side up” image when the object is less than one focal length away.  If the object is twice the distance, the image will appear Upside down & smaller  A convex mirror will produce an image that is right side up & smaller.

25. Concave A Concave mirror or lens is curved inward towards the center.  Parallel light rays that pass through a concave mirror are reflected to a focal point

26. Concave/Convex

27. Focal Point The rays striking a concave mirror cross and then move apart again. The point at which the rays meet is called the focal point of the mirror. P. 597

28. Light Waves and Refraction

29. Light Waves Light Waves move at different speeds through different Mediums.  A ray of light will slow down when it moves from air into the denser medium of a pond.  The amount &direction a light ray bends when it enters a new medium depend on how dense the medium is.  A light wave enters a new medium at an angle other than 90º, the wave will turn toward the normal.

30. Electromagnetic Waves Electromagnetic Waves from a star will travel through empty space, they travel in straight lines because the medium has not changed.

31. A medium can refract light Some light rays reflect off the surface of glass. Refraction occurs when a wave strikes a new medium—such as the window—at an angle other than 90˚ and keeps going forward in a slightly different direction.

32. Refraction of Light Page 600 Waves moving at an angle into a denser medium turns toward the normal. Waves moving at an angle into a thinner medium turn away from the normal

33. Refraction and Rainbows Rainbows are caused by Refraction and reflection of Light through spherical water Drops, which acts as prisms. Only one color reaches Your eye from each drop. Red appears at the top of a Rainbow because it is coming From higher drops, while violet Comes from lower drops.

34. Shape determines how lenses from images Just as a curved mirrors distort images, certain transparent mediums called lenses alter what you see through them. A lens is a clear optical tool that refracts light. Different lenses refract light in different ways and form images useful for a variety of purposes.

35. Convex & Concave Lenses A convex lens causes parallel light rays to meet at a focal point A concave lens causes parallel light rays to spread out. Page 601 & 602

36. Images Formed by Lenses Notice the distance between the penguin and the lens in the illustration on page 602. The distance is measured in terms of a focal length, which is the distance from the center of the lens to the lens’s focal point.

37. To summarize If you look at an object through a concave lens, you’ll see an image of the object that is right side up and smaller than the object normally appears. If you look at an object through a convex lens, the image could be formed upside down and larger if two focal lengths away. Or it will appear right side up and larger if one focal length away.

38. How does a camera lens form an image A camera lens uses refraction to focus light on the film, or in a digital camera. When a ray of light passes from a less dense to a more dense medium (such as from air to glass) it slows down. If it strikes the glass surface at an angle, it is also bent a little, and this is called refraction. When it passes back into air, it speeds up again, and is again refracted if the surface is at an angle.

39. 18.3 The Eye is a Natural Optical Tool Objectives Recognize how the eye depends on natural lenses. Explain how artificial lenses can be used to correct vision problems.

40. Eyes gathers and focuses light Eyes transmit light, refract light, and respond to different wavelengths of light. Eyes contain natural lenses that focus images of objects and then sends signals to the brains. The brain interprets these signals as shape, brightness, and color.

41. How Light Travels through the Human Eye 1.Light enters the eye through the cornea, a transparent membrane that covers the eye. The two parts of the eye that refract light are the CORNEA AND LENS

42. Retina The retina detects an image and send signals to the brain The CORNEA acts like a convex lens The lens adjusts to focus an image on the retina

43. How Light Travels through the Human Eye 2.Light continues through the pupil, a circular opening that controls how much light enters the eye. The pupil is surrounded by the iris, which opens and closes to change the size of the pupil.

44. How Light Travels through the Human Eye 3.Next, the light passes through the lens. It refracts light to make fine adjustments for near or far objects. The lens is connected to tiny muscles that contract and relax to control the amount of refraction that occurs and to move the focal point.

45. How Light Travels through the Human Eye 4. The light then passes through he clear center of the eye and strikes the retina. The retina contains specialized cells that respond to light. Some of these cells sends signals through the optic nerve to the brain.

47. How the Eye Forms Images For a complete image to be formed in the eye and communicated to the brain. The Retina plays a very important role.

48. Retina: Rod Cells Rod cells distinguish between white and black and shades of gray. Help in night vision.

49. Retina: Cone Cells Cone cells- respond to different wavelength of light so they detect color. There are three types: Red, Blue, and Green. They respond to other colors by using a combination of the three.

50. Cameras Just like our eyes have to focus on an image, we must move the lens of a camera to focus an image onto film

51. Corrective Lenses can Improve Vision How many of you wear contacts or glasses? About 36 million wear contact lenses When the image formed by the lens of the eye does not fall exactly on the retina. A blurry image is formed. Artifical lenses are used to correct this problem.

52. Farsighted Objects are clearer to a farsighted person when the objects are farther away. It occurs when the lens of the eye focuses an object’s image behind the retina.This can be caused by aging. A person who is farsighted can be helped by a convex lens, that make light rays converge farther towards the retina.

53. Corrective Lenses Nearsighted cannot see objects clearly unless they are near. It occurs when the lens of the eye focuses the image in front of the retina. A person who is nearsighted wears glasses to spread light out so that the image is focused on the retina.

54. Surgery Doctors can use surgical procedures to shape the cornea. To correct nearsightedness, surgeons remove tissue from the center of the cornea. To correct farsightedness, surgeons remove tissue from around the edge of the cornea. http://www.youtube.com/watch?v=dZZguJ NitnU http://www.youtube.com/watch?v=dZZguJ NitnU

55. Contacts Contact lenses also correct vision by changing the way the cornea refracts light. CONTACTS work with the cornea and tears to act as a single lens. This is only a temporary fix.

56. Objectives Identify sources of EM waves Recognize how EM waves transfer energy Describe how different EM waves are used Observe how to detect visible light Explain how visible light is produced Describe bioluminescence Identify types of artificial light Recognize how light waves interact with materials Recognize why objects have color & how colors are produced

57. Visible Light Spectrum

58. Electromagnetic Waves Electromagnetic waves can be converted into useful forms (Microwave ovens)

59. Incandescence & Bioluminescence Incandescence is the production of light by materials at high temperatures. Some organisms can produce their own light, this is called bioluminescence.

60. Artificial Lighting There are many types of artificial lighting (Textbook Page 571-572)

61. Light Waves Light can be transmitted, reflected, absorbed or scattered. A prism is a tool that uses refraction to spread out different wave lengths of light

62. Polarization Polarization is a quality of light in which all of its waves vibrate in the same direction