G10 Science Q2-W6-7- Plane Curve Mirrors.pptx

Plane Curve Mirror Mirror and Lenses

1. PLANE, CURVE MIRRORS and LENSES 1 PREPARED BY: TYPE YOUR NAME HERE

2. PLANE MIRRORS a flat surface on which a straight line joining any two points on it would wholly lie. 2 used in dressing rooms, bedrooms, bathrooms, nad in cars.

3. PLANE MIRRORS 3

4. PLANE MIRRORS CHARACTERISTICS: In the case of plane mirrors, the image is said to be a  virtual image .  Virtual images are images that are formed in locations where light does not actually reach.  Image is upright, virtual, and of the same size as the object. 4

5. PLANE MIRRORS 5

6. In summary, the image formed by the plane mirror has the following characteristics: A. The image distance is equal to the object distance B. The image is virtual, upright and of the same size as the object. C. The image is laterally reversed. 6

7. CURVED or SPHERICAL MIRRORS kind of mirror with a curved reflecting surface. have surfaces that are shaped like part of a sphere. The surface may be either  convex   (bulging outwards) or  concave (bulging inwards). 7

8. CURVED or SPHERICAL MIRRORS CONVEX MIRROR is a curved mirror in which the reflective surface bulges toward the light source. Inner surface reflects light 8

9. CONVEX MIRROR 9

10. CONCAVE MIRROR forms an enlarged image depending upon the position of the object. a curved surface with reflection coating outer part of the curve is called a   concave mirror 10

11. CONCAVE MIRROR 11

12. Parts of Convex and Concave Mirrors There are mirrors terminology which you should know. They are the following: 1. Vertex (V) is the middle portion of the mirror. 2. Center of curvature (C) is the center of the sphere of which the curved mirror is a part. 3. Radius of curvature (r) is the distance of the center of curvature from the vertex. 4. Principal axis (P) is the line drawn passing through the vertex and the center of curvature. 12

13. 5. Secondary axis (S) is a line drawn through the center of curvature to any part in the mirror. 6. Aperture (A) is the opening of the mirror. 7. Focus (F) is the point where the reflected rays meet. 8. Focal length (f) is the distance between the focus and the vertex. 13

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15. How do converging and diverging mirrors differ? 15

16. IMAGE FORMATION OF SPHERICAL MIRRORS 16

17. CONCAVE MIRRORS: 17

18. CONCAVE MIRRORS: 18

19. The image formed by convex mirror is never real because the reflected rays spread out from the mirror. 19

20. Ray diagrams are used to depict the image formation by tracing the path of light rays i.e. incident rays and reflected rays. They are drawn in order for anyone to view a point on the image of an object. These ray diagrams depend on the position of the object. 20

21. Ray Diagrams for a Concave Mirror 21

22. 22 The object is located beyond C What are the characteristics of the image formed?

23. 23 The object is located at C What are the characteristics of the image formed?

24. 24 The object is located Between C and F

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27. 27 For convex mirror , the object is placed a nywhere in front of the mirror… What will be the Characteristics o f the image formed?

28. 28 1. Pick a point on the top of the object and draw two incident rays traveling towards the mirror. Step-by-Step Procedure for Drawing Ray Diagrams The method of drawing ray diagrams for convex mirrors is described below.

29. 29 2. Once these incident rays strike the mirror, reflect them according to the  two rules of reflection  for convex mirrors. Step-by-Step Procedure for Drawing Ray Diagrams The method of drawing ray diagrams for convex mirrors is described below. The ray that travels towards the focal point will reflect and travel parallel to the principal axis . Use a straight edge to accurately draw its path. The ray that traveled parallel to the principal axis on the way to the mirror will reflect and travel in a direction such that its extension passes through the focal point.

30. 30 3. Locate and mark the image of the top of the object. Step-by-Step Procedure for Drawing Ray Diagrams The method of drawing ray diagrams for convex mirrors is described below. The image point of the top of the object is the point where the two reflected rays intersect. Since the two reflected rays are diverging, they must be extended behind the mirror in order to intersect. Using a straight edge, extend each of the rays using dashed lines. Draw the extensions until they intersect. The point of intersection is the image point of the top of the object.

31. The diagrams below show that in each case, the image is - located behind the convex mirror - a virtual image - an upright image - reduced in size (i.e., smaller than the object) 31

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33. Its your turn to do it… Activity: Are You L.O.S.T. after Reflection? 33

34. Simple Uses of Concave Mirrors 34

35. Shaving and Makeup Mirrors 35

36. Concave mirrors are often used as shaving mirrors and makeup mirrors . Objects held close are reflected in a concave mirror as a magnified image. When the mirror is held close to the face, an enlarged image of the skin can be seen. For shaving purposes, this allows you to see if any hair has been missed and to make sure that all hairs have been cut to the same length. For makeup purposes, it allows you to make sure all the skin on the face is covered and blended evenly. 36

37. Headlights Concave mirrors are used in motor vehicle headlights to send out strong beams of light. Instead of reflecting an image, they are used to focus the light from the bulb. Rays of light from the bulb are reflected off the concave mirror, creating a strong beam that shines on the road. 37

38. Microscopes Near the base of a microscope, you may find a concave mirror mounted so it can be turned in any direction. Concave mirrors are used in microscopes to collect light from a lamp, shining it up onto a slide containing a specimen so it can be viewed through a magnification lens. It is important to never point the mirror toward the sun to collect light; the sunlight would be focused and could blind the person looking through the lens of the microscope. 38

39. Telescopes Large telescopes traditionally have a concave mirror at one end. Similar to how a concave mirror works in a microscope, the concave mirror in the telescope collects light. Instead of shining the light up to a specimen, it shines the light from distant stars onto a flat mirror. The viewer looks through the lens on the eyepiece of the telescope and sees the reflection on the mirror, allowing a view of stars that the naked eye is unable to see. 39

40. Dentist use concave mirror so that he/she will be able to see the magnified view of patients affected teeth  40

41. Simple Uses of Convex Mirrors 41

42. Most of the passenger side mirror on any vehicle, especially car, is the convex mirror. In some parts of the country, such mirrors come with precaution message, to warn drivers of the distorting effects of it. These mirrors are preferred in vehicles, as they provide a diminished and upright image. 42

43. Moreover,  these mirrors provide a wider view , when they are curved in an outward direction. These mirrors are found in hallways of different buildings, like schools, hospitals, hotels, apartment buildings and stores. 43

44. Convex mirrors provide visibility at blind spots, such as hallway corners and driveway exits. 44

45. Convex mirrors are used in some other areas, as well. Listed below, are some of the additional zones, where such fish eye mirrors are used: The round form of fish eye mirrors was considered as a mark of luxurious lifestyle, which started from 15th century. 45

46. 46 Due to its larger area covering capabilities, these mirrors have now gained worldwide popularity. Not just in common daily lives, but these mirrors are now used as the best safety product for preventing road accidents. The stands of these mirrors are mainly constructed using poly carbonate or metals, with varying curvature degree.

47. During most of the time, these mirrors are used in automated teller machines, as a handy and simple security feature. 47

48. They are even used as a special inspection device, where it is hard to reach. Here, the mirrors are mounted on a proper rod and extended with lights under the object to be viewed. Some common examples are clocks, car repair or appliances. 48

49. LENS A spherical lens is a piece of glass or transparent material that has at least one spherical surface. 49

50. Lenses – An application of refraction Refraction is the bending of light (it also happens with sound, water and other waves) as it passes from one transparent substance into another.

51. Lenses – An application of refraction This bending by refraction makes it possible for us to have lenses, magnifying glasses, prisms and rainbows. Even our eyes depend upon this bending of light. Without refraction, we wouldn’t be able to focus light onto our retina (A light-sensitive tissue lining the inner surface of the eye).

52. There are two main types of lenses: • convex lenses —these curve outwards and are fatter in the middle • concave lenses —these curve inwards (a little like a cave) and are thinner in the middle. Convex lenses Concave Lenses

53. A converging lens (Convex) takes light rays and bring them to a point. A diverging lens (concave) takes light rays and spreads them outward.

54. LENS TERMINOLOGY CONVEX LENS In a convex lens, an incoming ray parallel to the principal axis is refracted through the principal focus (F). The optical center of the lens is the point which all light rays pass without being bent. When beam of parallel rays falls on a convex lens, the rays are refracted and converge to a point called principal focus Focal length (f) is the distance from the optical center of the lens to the principal focus.

55. Concave Lens In a concave lens, an incoming ray parallel to the principal axis is refracted so that it appears to come from the principal focus (F).

56. Movement of Light through a Lens The distance from the centre line (plane) of the lens to the principal focus is called the focal length of the lens. A ray passing through the centre of either type of lens is unaffected. As with all images, rays of light that come from a part of the object come together again at that same part of the image.

57. Focal Length The greater the curvature of a lens, the more it bends light and hence the shorter the focal length.

58. Image type and Location Convex lenses produce two different types of images, depending on where the object is located. If the object is at a distance greater than the focal length of the lens, a real image is formed. A real image can be projected onto a screen

59. Convex Lenses If the object is at a distance less than the focal length of the lens, a virtual image is formed. This image can’t be projected onto a screen.

60. Concave Lenses Concave lenses produce only virtual images.

61. Finding the focal length Rays coming into a lens from a distant object are almost parallel and form an image very close to the focus. We can then measure the distance from lens to image to determine the focal length of the lens.

62. 62 Step-by-Step Method for Drawing Ray Diagrams The method of drawing ray diagrams for double convex lens is described below. The description is applied to the task of drawing a ray diagram for an object located  beyond  the  2F point  of a double convex lens. 1. Pick a point on the top of the object and draw three incident rays traveling towards the lens.

63. 63 Step-by-Step Method for Drawing Ray Diagrams 2. Once these incident rays strike the lens, refract them according to the  three  rules  of refraction  for converging lenses.

64. 64 Step-by-Step Method for Drawing Ray Diagrams 2. Once these incident rays strike the lens, refract them according to the  three  rules  of refraction  for converging lenses. Any incident ray traveling parallel to the principal axis of a converging lens will refract through the lens and travel through the focal point on the opposite side of the lens. Any incident ray traveling through the focal point on the way to the lens will refract through the lens and travel parallel to the principal axis. An incident ray that passes through the center of the lens will in effect continue in the same direction that it had when it entered the lens.

65. 65 Step-by-Step Method for Drawing Ray Diagrams 3. Mark the image of the top of the object. The image point of the top of the object is the point where the three refracted rays intersect. All three rays should intersect at exactly the same point. This point is merely the point where all light from the top of the object would intersect upon refracting through the lens.

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68. 68 A virtual image is formed if the object is located less than one focal length from the converging lens.

69. 69 For the case of the object located at the focal point (F), the light rays neither converge nor diverge after refracting through the lens. As shown in the diagram above, the refracted rays are traveling parallel to each other. Subsequently, the light rays will not converge to form a real image; nor can they be extended backwards on the opposite side of the lens to intersect to form a virtual image. So how should the results of the ray diagram be interpreted? The answer: there is no image!!

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71. 71 Any incident ray traveling parallel to the principal axis of a diverging lens will refract through the lens and travel  in line with  the focal point (i.e., in a direction such that its extension will pass through the focal point). Any incident ray traveling towards the focal point on the way to the lens will refract through the lens and travel parallel to the principal axis. An incident ray that passes through the center of the lens will in effect continue in the same direction that it had when it entered the lens. THREE SIMPLE  RULES  OF REFRACTION FOR  DOUBLE CONCAVE LENSES

72. 72 The method of drawing ray diagrams for a double concave lens is described below. 1. Pick a point on the top of the object and draw three incident rays traveling towards the lens.

73. 73 The method of drawing ray diagrams for a double concave lens is described below. 2. Once these incident rays strike the lens, refract them according to the  three  rules  of refraction  for double concave lenses. The ray that travels towards the focal point will refract through the lens and travel parallel to the principal axis. The ray that traveled parallel to the principal axis on the way to the lens will refract and travel in a direction such that its extension passes through the focal point on the object's side of the lens. The ray that traveled to the exact center of the lens will continue to travel in the same direction. Place arrowheads upon the rays to indicate their direction of travel.

74. 74 The method of drawing ray diagrams for a double concave lens is described below. 3. Locate and mark the image of the top of the object.

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