# Ch 23 vocab

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1. Ray model
A model that assumes light travels in rays
2. Ray
Straight-line path
3. Geometric optics
The subject of light acting as a ray with reflection, refraction, and the formation of images by mirrors and lenses
4. Angle of incidence
The angle an incident ray makes with the normal (perpendicular) to the surface
5. Angle of reflection
The angle the reflected ray makes with the normal
6. Law of reflection
The angle of reflection equals the angle of incidence
7. Diffuse reflection
When light hits a rough surface and is reflected in many directions
8. Specular reflection
When light hits a smooth surface and reflects in one direction
9. Image
10. Virtual image
An optical image formed by the apparent divergence of rays from a point, rather than their actual divergence from a point (when it doesn't actually focus, but our brain connects the dots)
11. Real image
An optical image formed by the actual divergence of rays from a point (never upright - opposite of virtual)
12. Convex
Spherical mirror with which the reflection takes place on the outer surface so that the center of the mirror surface bulges out
13. Concave
A mirror where the reflecting surface is on the inner surface so that the center shrinks away (like a cave)
14. Focus
Where reflected parallel rays cross each other
15. Principal axis
The straight line perpendicular to the curved surface at it's center
16. Focal point
• Where incident parallel rays come to a focus after reflection
• Also the image point for an object infinitely far away along the principal axis
17. Focal length
Distance between the focal point and the center of the mirror
18. Paraxial rays
Rays that make a small angle with the principal axis, so that they reflect at F
19. Spherical abberation
When rays from an image pass through the outer regions of the lens or mirror and are brought to a focus at a different point from those that pass through the center of the lens.
20. Do
Object distance, distance of the object from the center of the mirror (x value)
21. Di
Image distance, distance of the image from the center of the mirror (x value)
22. Ho
Object height, height of the object from the center of the mirror (y value)
23. Hi
Image height, height of the image from the center of the mirror (y value)
24. Mirror equation
• 1/do + 1/di = 1/f
• Where f is the focus, or r/2.
25. Magnification
"m", the height of the image divided by the hight of the object (hi/ho). This is also (-di/do).
26. Index of refraction
The ratio of the speed of light in a vacuum to the speed v in a given material. Denoted as n.
27. Refraction
When a ray of light changes direction as it enters a new medium
28. Angle of refraction
The angle the refracted ray makes with the normal to the surface
29. Snell's law
The angle of refraction depends on the speed of light in the two media and on the incident angle, also written as n[1]sint[1] = n[2]sint[2].
30. Law of refraction
Snell's law, or n[1]sint[1] = n[2]sint[2]
31. Critical angle
The incident angle at which the refracted ray would skim the surface, meaning the angle of refraction would be 90 degrees.
32. Total internal reflection
• When there is no refracted ray, all of the light is reflected
• Only occurs when the second medium has a lower index of refraction
33. Fiber optics
Total internal reflection used with tiny fibers as thin as a few micrometers in diameter
34. Converging lens
A lens that is thicker in the center than at the edges, which will make parallel rays converge to a point
35. Diverging lens
A lens that is thinner in the center than at the edges, and make parallel light diverge
36. Thin lens equation
Same as the mirror equation, 1/do = 1/di = 1/f
37. Sign conventions
• Focal length: pos for converging, neg for diverging
• Di: pos if image is on opposite side of the lens, neg if same side
• Hi: pos if upright, neg if inverted

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 Author: megame623 ID: 152338 Filename: Ch 23 vocab Updated: 2012-05-05 18:52:26 Tags: physics vocab Folders: Description: Ch 23, geometric optics Show Answers:

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