 | Term | Definition |
| |
light year |
the distance light travels in one year |
| |
Alpha Centauri |
closest star to us that is 4 light years away |
| |
light |
a type of energy that is emitted by accelerating electric charge. It consists of electric and magnetic energy. |
| |
transparent |
when an object is able to absorb and then reemit light energy. Ex.) glass, water |
| |
light ray |
a straight beam of light |
| |
shadow |
when a ray is blocked by an opaque object |
| |
umbra |
complete shadow |
| |
penumbra |
partial shadow |
| |
solar eclipse |
occurs when the moon is in front of the sun |
| |
lunar eclipse |
occurs when the earth is between the moon and the sun (a full moon) |
| |
3 things light can do when it strikes an object |
reflect, pass through, be absorbed |
| |
photon |
a massless bundle of electromagnetic particles |
| |
Photoelectric Theory |
Einstien's theory about photons |
| |
Greeks |
thought that light consisted of tiny particles, which could enter the eye to create the sensation of vision |
| |
Socrates, Eucid, and Plato |
thought that vision resulted from streamers or filaments emitted by the eyes making contact with an object |
| |
Empedocles and Christian Huygens |
thought that light travels in waves |
| |
dual nature of light |
light consists of both waves and particles |
| |
Olaus Roemer |
measure speed of light with Io and its rotation period |
| |
Christian Huygens |
figured out that Io was late, not the moon |
| |
Albert Michelson |
measured speed of light with mirrors |
| |
electromagnetic wave |
wave that is partly electric and partly magnetic ex.) light, radio waves, microwaves, x-rays |
| |
electromagnetic spectrum |
range of electromagnetic waves, consisiting of radio waves, microwaves, infared, light, ultraviolet rays, X-rays, and gamma rays |
| |
infared |
electromagnetic waves of frequencies lower that the red of visible light |
| |
ultraviolet |
electromagentic waves of frequencies higher than those of violet |
| |
polarization |
the aligning of vibrations in a transverse wave, usually by filtering out waves of other directions |
| |
incandescent light blub |
light bulb that gives off infared waves, golden light, and is "old-fashioned" |
| |
florescent light blub |
light blub that gives off ultraviolet waves, bright light, and is "green" |
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