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UNIT 8 Light and Optics

UNIT 8 Light and Optics. ConcepTest 35.2b Mirror II. 1) same as your height 2) less than your full height but more than half your height 3) half your height 4) less than half your height 5) any size will do.

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UNIT 8 Light and Optics

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  1. UNIT 8Light and Optics

  2. ConcepTest 35.2bMirror II 1) same as your height 2) less than your full height but more than half your height 3) half your height 4) less than half your height 5) any size will do You stand in front of a mirror. How tall does the mirror have to be so that you can see yourself entirely?

  3. ConcepTest 35.2bMirror II 1) same as your height 2) less than your full height but more than half your height 3) half your height 4) less than half your height 5) any size will do You stand in front of a mirror. How tall does the mirror have to be so that you can see yourself entirely? Trace the light rays from the image’s foot to the mirror and then to the eye. Since we know thatqi = qr , you need a mirror only half your size.

  4. ConcepTest 35.2c Mirror III 1) No. 2) Yes. 3) Depends on the mirror. 4) Depends on the person. Does this depend on your distance from the mirror?

  5. The further you step back, the smaller the incident and reflected angles will be. But the rays will still be reflected at the same points, so the ray from the foot will still be reflected at mid-height. ConcepTest 35.2c Mirror III 1) No. 2) Yes. 3) Depends on the mirror. 4) Depends on the person. Does this depend on your distance from the mirror?

  6. Thursday February 16th Light and Optics

  7. Thursday, February 16 TODAY’S AGENDA • Curved Mirrors Concave • Hw: Practice B (all) p462 UPCOMING… • Fri: NO School • Mon: Curved Mirrors Convex • Tue: Problem Quiz #1 • Color and Polarization • Wed: Refraction

  8. Chapter 13 Light and Reflection

  9. Formation of Images by Spherical Mirrors Spherical mirrors are shaped like sections of a sphere, and may be reflective on either the inside (concave) or outside (convex).

  10. Formation of Images by Spherical Mirrors Rays coming from a faraway object are effectively parallel.

  11. Formation of Images by Spherical Mirrors Parallel rays striking a spherical mirror do not all converge at exactly the same place if the curvature of the mirror is large; this is called spherical aberration.

  12. Formation of Images by Spherical Mirrors If the curvature is small, the focus is much more precise; the focal point is where the rays converge.

  13. Formation of Images by Spherical Mirrors Using geometry, we find that the focal length is half the radius of curvature: Spherical aberration can be avoided by using a parabolic reflector; these are more difficult and expensive to make, and so are used only when necessary, such as in research telescopes.

  14. Formation of Images by Spherical Mirrors We use ray diagrams to determine where an image will be. For mirrors, we use three key rays, all of which begin on the object: • A ray parallel to the principal axis; after reflection it passes through the focal point. 2. A ray through the focal point; after reflection it is parallel to the principal axis. • 3. A ray through the focal point; after reflection it is parallel to the principal axis.

  15. Images Formed by Spherical Mirrors center of curvature = C = radius R Principle Focal Point Concave Mirror R C

  16. Images Formed by Spherical Mirrors Image Characteristics Type: Real or Virtual Size: Larger, Smaller, or Same (as the Object) Upright or Inverted Orientation: do: always positive real is positive; virtual is negative di: f: In front of mirror is positive; Behind mirror is negative

  17. Images Formed by Spherical Mirrors parallel ray real central ray smaller focal ray inverted image Concave Mirror Image Characteristics Case #1 image found between C and f

  18. Images Formed by Spherical Mirrors real same inverted image Concave Mirror Image Characteristics Case #2 image found at the C

  19. Images Formed by Spherical Mirrors real larger inverted image Concave Mirror Image Characteristics Case #3 C image found beyond C

  20. Images Formed by Spherical Mirrors Concave Mirror Image Characteristics Vampire case Case #4 No image C

  21. Images Formed by Spherical Mirrors Make-up case virtual image larger upright Concave Mirror Case #5 C Image Characteristics image found behind mirror

  22. Images Formed by Spherical Mirrors Produces Parallel Rays of Light Concave Mirror Light Source at the Focal Point

  23. Images Formed by Spherical Mirrors di do f ho hi Concave Mirror

  24. Images Formed by Spherical Mirrors di do f ho hi Concave Mirror

  25. Images Formed by Spherical Mirrors =

  26. Images Formed by Spherical Mirrors

  27. Images Formed by Spherical Mirrors Virtual Image Concave Mirror f

  28. Images Formed by Spherical Mirrors do di hi ho f Concave Mirror

  29. Images Formed by Spherical Mirrors do di hi ho M > 1 Larger f M < 1 Smaller M= M = 1 Same M + Upright M - Inverted Concave Mirror Magnification

  30. Images Formed by Spherical Mirrors A object is placed between a concave mirror and its focal point. The image formed is (A) virtual and inverted. (B) virtual and upright. (C) real and upright. (D) real and inverted.

  31. Images Formed by Spherical Mirrors (Problem) 3 = = M= A mirror at an amusement park shows an upright image of any person who stands 1.4 m in front of it. If the image is three times the person’s height, what is the radius of curvature? The image characteristics identify the case as concave #5 (larger, virtual, and upright). di = -4.2 m

  32. Images Formed by Spherical Mirrors If you stand in front of a concave mirror, exactly at its focal point, (A) you will see your image at your same height. (B) you won't see your image because there is none. (B) you will see your image, and you will appear smaller. (C) you will see your image and you will appear larger.

  33. END

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