Lens and Mirrors [Autosaved] for Grade 10.pptx

Grade 10 science

1. LIGHTS: MIRRORS AND LENSES Enhanced Science 10

2. OUTLINE OF TOPICS Lesson 1 – Plane Mirror Lesson 2 – Mirrors: Concave and Convex Lesson 3 – Lenses: Concave and Convex

3. Predict the qualitative characteristics (orientation, type, and magnification) or images formed by plane and curved mirrors and lenses. MELC

4. Reflection is a fundamental property of light, and it refers to the bouncing back of light when it encounters a surface. Reflection Properties of Light

5. SPECULAR VS DIFFUSE TYPES OF REFLECTION Light reflects from a smooth surface at the same angle as it hits the surface. For a smooth surface, reflected light rays travel in the same direction. This is called specular reflection. For a rough surface, reflected light rays scatter in all directions. This is called diffuse reflection.

6. The angle of incidence (the angle between the incident ray and the normal, which is an imaginary line perpendicular to the surface) is equal to the angle of reflection (the angle between the reflected ray and the normal). This principle is known as the Law of Reflection and holds true for smooth surfaces.

7. Incident Ray The incident ray is the incoming ray of light that strikes the surface. Normal Line The normal line is an imaginary line drawn perpendicular to the surface at the point of incidence. The angles of incidence and reflection are measured relative to this line.

8. Angle of Incidence and Reflection The angles of incidence and reflection are measured with respect to the normal line, providing a consistent way to describe the reflection process Reflected Ray The reflected ray is the ray of light that bounces off the surface.

9. Multiple Reflections Multiple reflections occur when light reflects more than once, such as in a series of mirrors arranged at different angles

10. How do mirrors interact with light?

11. Converging and Diverging Mirrors

12. Which is which?

13. Converging vs Diverging Mirror

14. Converging vs Diverging Mirror A converging mirror focuses light rays to a point, while a diverging mirror spreads them out.

15. Converging vs Diverging Mirror Converging mirrors, also known as concave mirrors, have a curved surface that bulges inward. When light rays hit the mirror, they are reflected inward and converge at a point called the focal point. The distance between the mirror and the focal point is called the focal length. Converging mirrors are commonly used in telescopes, cameras, and headlights.

16. Converging vs Diverging Mirror Diverging mirrors, also known as convex mirrors, have a curved surface that bulges outward. When light rays hit the mirror, they are reflected outward and diverge, or spread out. The focal point of a diverging mirror is imaginary, as the reflected rays never actually converge. Diverging mirrors are commonly used in rear-view mirrors and security mirrors.

17. Converging vs Diverging Mirror The difference between converging and diverging mirrors lies in their curvature and the way they reflect light. Converging mirrors focus light rays to a point, while diverging mirrors spread them out. This difference in reflection is due to the different shapes of the mirrors. Converging mirrors have a concave shape, while diverging mirrors have a convex shape. Understanding the properties of converging and diverging mirrors is important in the study of optics and the design of optical instruments.

18. The Anatomy of a Curved Mirror

19. If a concave mirror is thought of as a slice of a sphere, where is the principal axis located? A. At the vertex B. At the center of curvature C. At the midpoint of the center of curvature and the vertex D. At the focal point

20. What is denoted by the letter C in the diagram of a concave mirror? A. Center of curvature B. Principal axis C. Focal point D. Vertex

21. Which point on the concave mirror's surface is denoted by the letter A in the diagram? A. Center of curvature B. Principal axis C. Vertex D. Focal point

22. The focal length of a concave mirror is: A. Equal to the radius of curvature B. One-half the radius of curvature C. Equal to the distance between the vertex and the center of curvature D. Equal to the distance between the vertex and the focal point

23. What is the distance from the mirror to the focal point known as? A. Radius of curvature B. Focal length C. Vertex D. Principal axis

24. If the focal point is the midpoint between the vertex and the center of curvature, what is the relationship between the focal length and the radius of curvature? A. They are equal B. The focal length is greater than the radius of curvature C. The focal length is less than the radius of curvature D. The focal length is one-half the radius of curvature

25. How is the line passing through the center of the sphere and attaching to the mirror in the exact center of the mirror referred to? A. Vertex B. Principal axis C. Center of curvature D. Focal point

26. Which point is the geometric center of the concave mirror? A. Center of curvature B. Principal axis C. Vertex D. Focal point

27. In which location would the center of curvature of a concave mirror be found? A. At the focal point B. At the vertex C. On the principal axis D. On the mirror's surface

28. What is represented by the distance from the vertex to the center of curvature in a concave mirror? A. Principal axis B. Focal length C. Radius of curvature D. Center of curvature

29. 1.) C. At the midpoint of the center of curvature and the vertex 2.) A. Center of curvature 3.) C. Vertex 4.) B. One-half the radius of curvature 5.) B. Focal length 6.) D. The focal length is one-half the radius of curvature 7.) B. Principal axis 8.) C. Vertex 9.) C. On the principal axis 10.) C. Radius of curvature

30. Spherical Mirrors Curved mirrors that have a spherical shape are called spherical mirrors. It can be thought of as a portion of a sphere that was sliced away and then silvered on one of the sides to form a reflecting surface. Concave mirrors were silvered on the inside of the sphere and convex mirrors were silvered on the outside of the sphere.

31. Ray Diagramming Technique If a concave mirror were thought of as being a slice of a sphere, then there would be a line passing through the center of the sphere and attaching to the mirror in the exact center of the mirror. This line is known as the  principal axis . 

32. Ray Diagramming Technique The point in the center of the sphere from which the mirror was sliced is known as the  center of curvature  and is denoted by the letter  C  in the diagram. The point on the mirror's surface where the principal axis meets the mirror is known as the  vertex  and is denoted by the letter  A  in the diagram. 

33. Ray Diagramming Technique The vertex is the geometric center of the mirror. Midway between the vertex and the center of curvature is a point known as the  focal point ; the focal point is denoted by the letter  F  in the diagram. The distance from the vertex to the center of curvature is known as the  radius of curvature  (represented by  R ).

34. Ray Diagramming Technique The radius of curvature is the radius of the sphere from which the mirror was cut. Finally, the distance from the mirror to the focal point is known as the  focal length  (represented by  f ). Since the focal point is the midpoint of the line segment adjoining the vertex and the center of curvature, the focal length would be one-half the radius of curvature.

35. What is the Focal Point? The focal point is the point in space at which light incident towards the mirror and traveling parallel to the principal axis will meet after reflection. The diagram at the right depicts this principle. In fact, if some light from the sun were collected by a concave mirror, then it would converge at the focal point.

36. What is the Focal Point?

37. Images formed by concave mirrors

38. Let us RECALL Light always follows the  law of reflection , whether the reflection occurs off a curved surface or off a flat surface. The task of determining the direction in which an incident light ray would reflect involves determining the normal to the surface at the point of incidence. For a concave mirror, the normal at the point of incidence on the mirror surface is a line that extends through the  center of curvature . Once the normal is drawn the  angle of incidence  can be measured and the reflected ray can be drawn with the same angle.

39. Let us RECALL At the point of incidence where the ray strikes the mirror, a line can be drawn perpendicular to the surface of the mirror. This line is known as a normal line. The normal line  divides the angle between the incident ray and the reflected ray into two equal angles .

40. Images formed by concave mirrors Depending on the object location, the image could be enlarged or reduced in size or even the same size as the object; the image could be inverted or upright; and the image will be in a specific region along the principal axis. 

41. Two Rules of Reflection for Concave Mirrors Light always reflects according to the law of reflection, regardless of whether the reflection occurs off a flat surface or a curved surface. Using reflection laws allows one to determine the image location for an object. The image location is the location where all reflected light appears to diverge from. Thus, to determine this location demands that one merely needs to know how light reflects off a mirror.

42. The two rules of reflection for concave mirrors: Any incident ray traveling parallel to the principal axis on the way to the mirror will pass through the focal point upon reflection. Any incident ray passing through the focal point on the way to the mirror will travel parallel to the principal axis upon reflection.

43. Step-by-Step Method for Drawing Ray Diagrams 1. Pick a point on the top of the object and draw two incident rays traveling towards the mirror. Using a straight edge, accurately draw one ray so that it passes exactly through the focal point on the way to the mirror. Draw the second ray such that it travels exactly parallel to the principal axis. Place arrowheads upon the rays to indicate their direction of travel.

44. Step-by-Step Method for Drawing Ray Diagrams 2. Once these incident rays strike the mirror, reflect them according to the two rules of reflection for concave mirrors. The ray that passes through the focal point on the way to the mirror 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 through the focal point. Place arrowheads upon the rays to indicate their direction of travel. Extend the rays past their point of intersection.

45. 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 two reflected rays intersect. If your were to draw a third pair of incident and reflected rays, then the third reflected ray would also pass through this point. This is merely the point where all light from the top of the object would intersect upon reflecting off the mirror. Of course, the rest of the object has an image as well and it can be found by applying the same three steps to another chosen point.

46. Step-by-Step Method for Drawing Ray Diagrams 4. Repeat the process for the bottom of the object. The goal of a ray diagram is to determine the location, size, orientation, and type of image that is formed by the concave mirror. Typically, this requires determining where the image of the upper and lower extreme of the object is located and then tracing the entire image. After completing the first three steps, only the image location of the top extreme of the object has been found. Thus, the process must be repeated for the point on the bottom of the object.

47. Image Formation for CONCAVE Mirrors

48. Image Formation for CONCAVE Mirrors

49. Let’s Practice

50. Let’s Practice

51. Images formed by convex mirrors

52. Image Formation In the animation above, an object is positioned above the principal axis of a concave mirror and somewhere beyond the center of curvature (C). The concave mirror will produce an image of the object which is inverted (positioned below the principal axis) and located between the center of curvature (C) and the focal point (F) of the mirror.

53. Image Formation Any person viewing this image must sight at this image position. The animation depicts the path of light to each person's eye. Different people are sighting in different directions; yet each person is sighting at the same image location. As seen in the animation, the image location is the intersection point of all the reflected rays.

54. Image Formation In the animation above, an object is positioned above the principal axis of a concave mirror and between the center of curvature (C) and the focal point (F). The concave mirror will produce an image of the object which is inverted (positioned below the principal axis) and located somewhere beyond the center of curvature (C) of the mirror.

55. Image Formation Any person viewing this image must sight at this image position. The animation depicts the path of light to each person's eye. Different people are sighting in different directions; yet each person is sighting at the same image location. As seen in the animation, the image location is the intersection point of all the reflected rays.

56. The Anatomy of the Lens

57. What is a lens? If a piece of glass or other transparent material takes on the appropriate shape, it is possible that parallel incident rays would either converge to a point or appear to be diverging from a point. A piece of glass that has such a shape is referred to as a lens.

58. Types of Lenses Lenses differ from one another in terms of their shape and the materials from which they are made.

59. Types of Lenses A converging lens is a lens that converges rays of light that are traveling parallel to its principal axis. Converging lenses can be identified by their shape; they are relatively thick across their middle and thin at their upper and lower edges.

60. Types of Lenses A double convex lens is symmetrical across both its horizontal and vertical axis. Each of the lens' two faces can be thought of as originally being part of a sphere. The fact that a double convex lens is thicker across its middle is an indicator that it will converge rays of light that travel parallel to its principal axis. A double convex lens is a converging lens.

61. Types of Lenses A diverging lens is a lens that diverges rays of light that are traveling parallel to its principal axis. Diverging lenses can also be identified by their shape; they are relatively thin across their middle and thick at their upper and lower edges.

62. Types of Lenses A double concave lens is also symmetrical across both its horizontal and vertical axis. The two faces of a double concave lens can be thought of as originally being part of a sphere. The fact that a double concave lens is thinner across its middle is an indicator that it will diverge rays of light that travel parallel to its principal axis. A double concave lens is a diverging lens.

63. The Language of Lenses If a symmetrical lens were thought of as being a slice of a sphere, then there would be a line passing through the center of the sphere and attaching to the mirror in the exact center of the lens. This imaginary line is known as the principal axis. A lens also has an imaginary vertical axis that bisects the symmetrical lens into halves. As mentioned above, light rays' incident towards either face of the lens and traveling parallel to the principal axis will either converge or diverge. If the light rays converge (as in a converging lens), then they will converge to a point.

64. The Language of Lenses This point is known as the focal point of the converging lens. If the light rays diverge (as in a diverging lens), then the diverging rays can be traced backwards until they intersect at a point. This intersection point is known as the focal point of a diverging lens. The focal point is denoted by the letter F on the diagrams below. Note that each lens has two focal points - one on each side of the lens. Unlike mirrors, lenses can allow light to pass through either face, depending on where the incident rays are coming from. Subsequently, every lens has two possible focal points.

65. The Language of Lenses The distance from the mirror to the focal point is known as the focal length (abbreviated by f). Technically, a lens does not have a center of curvature (at least not one that has any importance to our discussion). However a lens does have an imaginary point that we refer to as the 2F point. This is the point on the principal axis that is twice as far from the vertical axis as the focal point is.