Science 8: Unit C

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Science 8 Unit C Light and Optics

• Topic 7 The Wave Model of Light

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Wave Model of Light

• Created by Christian Huygens in the 1600s.
• Light travels as waves of energy, not particles
  of matter.
• Light travels in transverse waves (eg. waves move
  up and down).

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Characteristics of Waves

• The highest part of the wave is called the crest,
  the lowest part is the trough.
• One crest and one trough together make up one
  wavelength measured in m.
• The color of light depends on the wavelength of
  the wave.
• The resting point of the wave (middle ground) is
  called the equilibrium.

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Characteristics of Waves Contd

• The amplitude of a wave is the distance from the
  equilibrium to the crest/trough. (its measured
  in m)
• The greater the amplitude the more intense the
  wave (brighter the light when it comes to light
  waves)

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Characteristics of Waves Contd

• Frequency is the number of wavelengths completed
  per second (or that move past a certain part)
• The unit for frequency is the hertz (Hz)
• To calculate the speed of a wave
• Speed of wave frequency of wave X wavelength of
  wave

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Frequency and Color

• The higher the frequency of a light wave, the
  smaller its wavelength and the more energy it
  contains.
• Eg1. Because red light is longer it is the first
  and last color of light to reach over the horizon
  during sun-up and sundown.
• Eg2. DVDs rely on a red laser to read
  information. The new Blu-Rays use blue lasers
  which can read more information because of their
  smaller wavelengths.

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Coherent and Incoherent Light

• White light contains light of many different
  wavelengths which can overlap and cancel each
  others colors. This is called incoherent light.
• Coherent light is light of all the same
  wavelength which amplifies the crests and troughs
  making the light more intense and of the same
  color. This is the kind of light used in lasers
  which have a wide range of applications.

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Green Laser