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Light and Optics

Light and Optics. What Can Y ou D iscover A bout Light?. Using the supplies that you have been given, make some of your own discoveries about light and draw diagrams with explanations showing what you discovered. You don’t need to know “why” you are seeing what you are seeing, only “what”.

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Light and Optics

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  1. Light and Optics

  2. UCSD: Physics 8; 2006 What Can You Discover About Light? • Using the supplies that you have been given, make some of your own discoveries about light and draw diagrams with explanations showing what you discovered. You don’t need to know “why” you are seeing what you are seeing, only “what”. • (Show demo of refraction with laser and broken stir stick) • (Try the optic nerve activity with Tweety and Sylvester)

  3. UCSD: Physics 8; 2006 Light and Color – Bill Nye • http://www.youtube.com/watch?v=gtgBHsSzCPE

  4. UCSD: Physics 8; 2006 1.1 Human Understanding of Light • Using your textbook (pgs. 176-181), create a timeline documenting the important discoveries about light throughout human history. Be sure to include who the person/people involved are, and what they discovered.

  5. UCSD: Physics 8; 2006 1.2 Optical Devices • An Optical Device is any technology that uses light. • 2 common optical devices are Microscopes (make small objects bigger) and Telescopes (make far objects closer). • Microscopes – use at least 2 lenses to increase the size of an object.

  6. UCSD: Physics 8; 2006 Optical Devices • Refracting telescopes – use 2 different sized lenses to collect and magnify light in order to make it seem like an object is larger than it is.

  7. UCSD: Physics 8; 2006 Optical Devices • Reflecting telescopes – use 2 different sized mirrors (one curved inwards) to collect and magnify light in order to make it seem like an object is larger than it is.

  8. UCSD: Physics 8; 2006 2.1 Ray Diagram and the Path of Light • Light always travels in straight lines from a light source • A Ray Diagram shows the direction that light travels using an arrow to indicate the direction of travel. • It travels in all directions until it is something gets in its way. The object will either reflect the light, absorb it or else allow the light to pass through it.

  9. UCSD: Physics 8; 2006 Examples of Ray Diagrams The arrow indicates the direction light travels

  10. UCSD: Physics 8; 2006 Ray Diagram and the Path of Light – Cont. • Opaque objects – Allow no light to pass though and absorb or reflect light that hits it • Ex – • Translucent Objects – Allow some light to pass through and some is absorbed • Ex – • Transparent Objects – Allow all light to pass though them • Ex -

  11. UCSD: Physics 8; 2006 Ray Diagram and the Path of Light – Cont. • Any object that emits its own light is said to be a LUMINOUS object. • Some examples of natural luminous objects are: • Some examples of human made luminous objects are: • Any object that reflects light but DOES NOT PRODUCE IT is said to be a NON-LUMINOUS object • Some examples of non-luminous objects are:

  12. UCSD: Physics 8; 2006 Reflection Lab • Reflection Lab.notebook • Reflection Lab Finished.notebook

  13. surface normal same angle Reflection • We describe the path of light as straight-line rays • Reflection off a flat surface follows a simple rule: • angle in (incidence) equals angle out (reflection) • angles measured from surface “normal” (perpendicular) • (Show Echalk reflection example) exit ray reflected ray incident ray

  14. UCSD: Physics 8; 2006 Regular and Diffuse Reflection

  15. Curved mirrors • What if the mirror isn’t flat? • light still follows the same rules, with local surface normal • used in telescopes, backyard satellite dishes, etc. • also forms virtual image (an image that is not real)

  16. Convex Mirrors • Curves outward • Smaller images but more can be seen • Virtual images – image is always right side up!!! • Use: Rear view mirrors, store security… CAUTION! Objects are closer than they appear!

  17. View kacleaveland's map Taken in a place with no name (See more photos or videos here) "Have you ever approached a giant concave mirror? See your upside-down image suspended in mid-air. Walk through the image to see a new reflection, right-side-up and greatly magnified. In the background you see reflected a room full of visitors enjoying other Concave Mirrors • Curves inward • May be real or virtual image

  18. UCSD: Physics 8; 2006

  19. For a real object between f and the mirror, a virtual image is formed behind the mirror. The position of the image is found by tracing the reflected rays back behind the mirror to where they meet. The image is upright and larger than the object. For a real object between f and the mirror, a virtual image is formed behind the mirror. The image is upright and larger than the object.

  20. For a real object between f and the mirror, a virtual image is formed behind the mirror. The position of the image is found by tracing the reflected rays back behind the mirror to where they meet. The image is upright and larger than the object. For a real object close to the mirror but outside of the center of curvature, the real image is formed between C and f. The image is inverted and smaller than the object. For a real object between C and f, a real image is formed outside of C. The image is inverted and larger than the object. For a real object between C and f, a real image is formed outside of C. The image is inverted and larger than the object.

  21. For a real object between f and the mirror, a virtual image is formed behind the mirror. The position of the image is found by tracing the reflected rays back behind the mirror to where they meet. The image is upright and larger than the object. For a real object close to the mirror but outside of the center of curvature, the real image is formed between C and f. The image is inverted and smaller than the object. For a real object between C and f, a real image is formed outside of C. The image is inverted and larger than the object. For a real object at C, the real image is formed at C. The image is inverted and the same size as the object. For a real object at C, the real image is formed at C. The image is inverted and the same size as the object.

  22. For a real object between f and the mirror, a virtual image is formed behind the mirror. The position of the image is found by tracing the reflected rays back behind the mirror to where they meet. The image is upright and larger than the object. For a real object close to the mirror but outside of the center of curvature, the real image is formed between C and f. The image is inverted and smaller than the object. For a real object close to the mirror but outside of the center of curvature, the real image is formed between C and f. The image is inverted and smaller than the object.

  23. For a real object at f, no image is formed. The reflected rays are parallel and never converge. What size image is formed if the real object is placed at the focal point f? For a real object at f, no image is formed. The reflected rays are parallel and never converge.

  24. Refraction • Light also goes through some things • glass, water, eyeball, air • The presence of material slows light’s progress • interactions with electrical properties of atoms • The “light slowing factor” is called the index of refraction • glass has n = 1.52, meaning that light travels about 1.5 times slower in glass than in vacuum • water has n = 1.33 • air has n = 1.00028 • vacuum is n = 1.00000 (speed of light at full capacity)

  25. UCSD: Physics 8; 2006 Refraction Lab • Refraction Lab.notebook

  26. A n1 = 1.0 n2 = 1.5 B Refraction at a plane surface • Light bends at interface between refractive indices • bends more the larger the difference in refractive index • (Show Echalkrefraction example)

  27. Video on the effects of refraction • http://www.youtube.com/watch?v=kc2o73FyN3I • 5:37 – 9:10

  28. Convex Lenses Thicker in the center than edges. • Lens that converges (brings together) light rays. • Forms real images and virtual images depending on position of the object • Images can be flipped and/or larger depending on the position of the lens The Magnifier

  29. Concave Lenses • Lenses that are thicker at the edges and thinner in the center. • Diverges light rays (spreads them apart) • All images arereducedor smaller because less light is hitting your eye The De-Magnifier

  30. UCSD: Physics 8; 2006 Practice! • Worksheet on Reflection and Refraction

  31. UCSD: Physics 8; 2006 The Human Eye

  32. UCSD: Physics 8; 2006 The Human Eye

  33. How You See • Near Sighted – Eyeball is too long and image focuses in front of the retina • Near Sightedness – Concave lenses expand focal length • Far Sighted – Eyeball is too short so image is focused behind the retina. • Far Sightedness – Convex lense shortens the focal length.

  34. UCSD: Physics 8; 2006 Eye Dissection • coweye dissection.pdf

  35. pinhole object image at film plane object image at film plane lens Cameras, in brief In a pinhole camera, the hole is so small that light hitting any particular point on the film plane must have come from a particular direction outside the camera In a camera with a lens, the same applies: that a point on the film plane more-or-less corresponds to a direction outside the camera. Lenses have the important advantage of collecting more light than the pinhole admits

  36. UCSD: Physics 8; 2006 Review Quiz • Light Rays Question Set.notebook

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