Light and Electromagnetic Waves

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Light and Electromagnetic Waves
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What are Electromagnetic Waves?

• Electromagnetic waves are waves which do not
  require matter to transfer energy.
• Electromagnetic waves need no medium like sound
  and water waves.
• Electromagnetic wave can travel in a vacuum
• Electromagnetic waves all travel 300,000,000
  meters per second in a vacuum

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Electromagnetic spectrum
The electromagnetic spectrum is the entire range
of electromagnetic waves arranged according to
their frequencies or wavelengths. Electromagnetic
waves all have different properties. But they all
travel the same speed what we call The speed
of light
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• Forms of electromagnetic radiation
• Visible light 400 to 700 nm This is the only
  form of electromagnetic wave visible to the human
  eye.
• Ultraviolet these cause our skin to darken
  (tan) and can even damage our skin. The ozone
  layer protects us from most UV radiation from the
  sun.
• X-rays these EM waves pass through much matter.
  It doesnt pass through dense bone, so it is
  useful in determining whether a bone is broken or
  not.

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• Gamma rays these EM waves are very penetrating
  and can severely damage cells.
• Infrared these waves are responsible for the
  heat we feel. Heat seeking missiles detect
  infrared sources such as tanks or aircraft.
• Microwaves these waves are used obviously to
  heat food. As these waves pass through food, it
  causes the particles to vibrate resulting in the
  heating of the food. Microwaves are also used in
  communication.
• Radio waves these waves include both TV and
  radio waves. Signals are transmitted and devices
  with antennas can receive the signals.

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• Wave Interactions
• Objectives
• Describe how waves behave when they meet an
  obstacle, pass into another medium, or pass
  through another wave.
• Explain what happens when two waves interfere.
• Distinguish between constructive interference and
  destructive interference.
• Explain how standing waves are formed
• SC Standards End-of Course Objectives
• PS-7.6 Summarize reflection and interference of
  both sound and light waves and refraction and
  diffraction of light waves.

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Reflection is the bouncing back of a wave as it
meets a surface or boundary. Diffraction is the
bending of a wave as it passes an edge or
opening. Refraction is the bending of a wave as
it passes from one medium to another. Interference
of waves occur when two or more waves exist in
the same place. Constructive interference occurs
when waves line up and the crests and troughs add
up. Destructive interference occurs when waves do
not line up and a crest is cancelled out by a
corresponding trough
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• The Nature of Light
• Objectives
• Recognize that light has both wave and particle
  characteristics.
• Relate the energy of light to the frequency of
  electromagnetic waves.
• Describe different parts of the electromagnetic
  spectrum.
• Explain how electromagnetic waves are used in
  communication, medicine, and other areas.
• SC End-of-Course Standards
• PS-7.5 Explain the characteristics of the
  electromagnetic spectrum, including range of
  wavelengths, frequency, energy, and propagation
  without a medium.
• PS-7.6 Summarize reflection and interference of
  both sound and light waves and refraction and
  diffraction of light waves.

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Particles or Waves Light produces interference
patterns like water waves. Light can be modeled
as a wave frequency, wavelength, and
velocity. Light can be modeled as a particle
(photon particle of light) The speed of light
depends on the medium. Unlike sound, light
travels fastest in a vacuum, the slow in more
denser states of matter.
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• Reflection and Color
• Objectives
• Describe how light reflects off smooth and rough
  surfaces.
• Explain the law of reflection.
• Show how mirrors form real and virtual images.
• Explain why object appear to be different colors.
• Describe how colors may be added or subtracted.
• SC End-of Course Standards
• PS-7.6 Summarize reflection and interference of
  both sound and light waves and refraction and
  diffraction of light waves.

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Reflection of light Light can be modeled as a
ray Light reflects off a smooth surface in one
direction.
Light reflects off rough surface in many
directions. Law of reflection
The angle of incidence
is equal to the angle of reflection
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Mirrors Flat mirrors form virtual images by
reflection Virtual image the apparent path of
light is detected rather than the actual path of
light. Curved mirrors distort images. Concave
mirrors create real images. Real image an
image of an object formed by many light rays
coming together in a specific location. Telescopes
use curved surfaces to focus light.
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Color Objects have color because they reflect
certain wavelengths of light. Objects appear red
because they absorb all colors except red which
is reflected. Objects which are green appear so
because they absorb all colors except green which
is reflected. Colors of light are additive.
Mixing colors of light results in white light
all colors reflected.
Pigments subtract color by absorbing wavelengths
of light. Mixing pigments results in all colors
being absorbed and no colors being reflected -
black
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• Refraction, Lenses, and Prisms
• Objectives
• Describe how light is refracted as it passes
  between mediums.
• Explain how fiber optics use total internal
  reflection.
• Explain how converging and diverging lenses work.
• Describe the function of the eye.
• Describe how prisms disperse light and how
  rainbows form.
• SC End-of-Course Standards
• PS-7.6 Summarize reflection and interference of
  both sound and light waves and refraction and
  diffraction of light waves.

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Refraction of light The bending of light as it
passes from one medium to another. Refraction
make objects appear to be in different
positions. Refraction in the atmosphere creates
mirages
Light can be refracted at the boundary between
two transparent mediums. Fiber optics use total
internal reflection. Prisms bend each color of
light at a different angle
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Lenses can magnify objects. Magnification is the
change in the size of an image compared to the
size of the object. Microscopes, telescopes, the
human eye, corrective lenses. Rainbows
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This concludes Module 8