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Physics Unit 9
Light
Term | Definition |
---|---|
electromagnetic wave | an energy-carrying wave emitted by a vibrating charge that is composed of oscillating electric and magnetic fields that regenerate one another |
electromagnetic spectrum | the range of electromagnetic waves extending in frequency from radio waves to gamma rays |
transparent | the property of materials to pass light in straight lines without being scattered |
opaque | the property of materials not to allow passage of light |
shadow | a shaded region that appears where light rays are blocked by an object |
umbra | the darker part of a shadow where all the light is blocked |
penumbra | a partial shadow that appears where some but not all light is blocked |
solar eclipse | an event in which the moon blocks light from the sun |
lunar eclipse | an event in which the moon passes into the shadow of the earth |
additive primary colors | red, blue, and green; when added in proportions, these 3 colors produce any other color in the spectrum; produce white when mixed equally |
complementary colors | any two colors of equal brightness that, when added, produce white light |
subtractive primary colors | magenta, yellow, cyan; when mixed in certain proportions, these 3 colors can reflect any other color in the spectrum |
reflection | the return of light rays from a surface |
Fermat's Principle of Least Time | light takes the path that requires the least time when it goes from one place to another |
Law of Reflection | the angle of reflection equals the angle of incidence |
refraction | the bending of an oblique ray of light when it passes from one transparent medium to another |
critical angle | the minimum angle of incidence inside a medium at which a light ray is totally reflected |
total internal reflection | the total reflection of light traveling within a denser medium when it strikes the boundary with a less dense medium at an angle larger than the critical angle |
converging lens | a lens that is thicker in the middle than at the edges and that refracts parallel rays to a focus |
diverging lens | a lens that is thinner in the middle than at the edges, causing parallel rays to diverge as if from a point |
virtual image | an image formed by light rays that do not converge at the location of the image; cannot be displayed on a screen |
real image | an image formed by light rays that converge at the location of the image; can be displayed on a screen |
aberration | distortion in an image produced by a lens, which to some degree is present in all optical systems |