Light and the Electromagnetic Spectrum

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Light and the Electromagnetic Spectrum
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Light Phenomenon

• Isaac Newton (1642-1727) believed light consisted
  of particles
• By 1900 most scientists believed that light
  behaved as a wave.

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The Electromagnetic Spectrum

• The electromagnetic spectrum represents the
  range of energy from low energy, low frequency
  radio waves with long wavelengths up to high
  energy, high frequency gamma waves with small
  wavelengths.

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• Visible light is a small portion of this
  spectrum. This is the only part of this energy
  range that our eyes can detect. What we see is a
  rainbow of colors.
• RedOrangeYellowGreenBlueIndigoViolet
• ROY G BIV

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• The colors we see in objects are the colors that
  are reflected, all other colors are absorbed. A
  red t-shirt appears red because red is reflected
  to our eyes and the other colors are absorbed.
• When all colors are being reflected we see white
  light (white isnt really a color)

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• When all wavelengths of light are being absorbed
  we see black (black also, isnt really a color)

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Absorption and Transmission

• Waves that are not reflected are either absorbed
• OR
• They are transmitted (pass through the substance)
  like light through a glass window or a pair of
  glasses

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Refraction
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Rainbows are Refracted Light

• When light waves from the sun pass through a
  droplet of water in the air, the light is
  refracted.
• The different colors of light travel at different
  speeds through the drop therefore the colors are
  refracted by different amounts RAINBOW

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Electromagnetic Waves

• Do not need a medium, CAN travel through empty
  space!
• Electromagnetic waves (light waves, microwaves,
  x-rays) can travel through empty space

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TRANSVERSE WAVES

• Transverse waves move perpendicularly to the
  direction the wave is moving
• Transverse waves are made up of CRESTS and
  TROUGHS
• Electromagnetic waves are examples of transverse
  waves.

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Properties of a Wave

• 1) AMPLITUDE
• 2) WAVELENGTH
• 3) FREQUENCY
• 4) SPEED

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Comparing Waves

• The frequency (v) of a wave is the number of
  waves to cross a point in a specified unit of
  time
• The wavelength- the distance from crest to crest
  on a wave
• Amplitude is the greatest distance a wave moves
  away from the rest position the greater the
  distance the more energy

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Wavelength

• The distance between any 2 corresponding points
  on a wave

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Amplitude
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Wavelength vs Frequency
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Properties of a Wave
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Reflection

• When a wave hits an object through which it
  cannot pass, it bounces back. This is called
  REFLECTION
• All waves can be reflected

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• The Law of Reflection

Angle of incidence Angle of reflection
In other words, light gets reflected from a
surface at the same angle it hits it.
The same !!!
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Refraction

• REFRACTION is the bending of waves when waves
  move from one medium to another.
• When a wave hits a new medium, it changes speed
  and the wavelength changes