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Light

  • Light is extremely fast. In a vacuum, light travels at
    c=299   792   458   m

    s
    ≈ 3·108   m

    s
    .
  • Depending on the material light is traveling through, its speed will change. Light travels through air close enough to c that we can use that value when working on problems.
  • Since light moves so fast, we can talk about very large distances using its speed as a reference point:
    Lightyear = c ·(1 year).
  • Normally waves need a medium to propagate through. This is not true of light, though. Light is able to travel without any medium (which is why the light of the sun can reach us, even though it's a wave).
  • The word "light" is sort of a misnomer. The visible spectrum we are used to seeing is only part of the much larger electromagnetic spectrum that makes up light.
  • Different kinds of electromagnetic waves have different frequencies. Higher frequencies carry more energy, lower frequencies carry less.

Light

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Physics (Theory and Application)