Warm Up

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Warm Up

• 1. Draw the EM spectrum.
• 2. Draw and label a transverse wave.
• 3. Draw a high frequency wave.
• 4. What are the different types of energy?
• 5. What are the 6 characteristics of life?

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Let there be LIGHT
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Light

• Light travels in straight lines at a speed of
  186,000 miles per second or 3.0 X 108 m/s.
• Light waves travel faster than sound waves!
• (Light energy from the sun travels through space
  , reaches earth, and some of it turns to heat
  energy and warms the earths air.)
• When light reaches an object, it is absorbed,
  reflected, or passes through it.

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Part 1 Properties of Light

• Light travels in straight lines

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• We see things because they reflect light into our
  eyes

Homework
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Just Passing Through What happens when light
strikes glass? Or waxed paper? Or a book?
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• If light is blocked by an object and a dark
  shadow is cast it is opaque.
• If some light passes through but not all and a
  light shadow is present it is translucent.
• If light travels through an object it is
  transparent

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What happens when light hits these objects?

• Glass of water
• School bus window
• Notebook paper
• Waxed paper
• Plastic wrap
• Tissue paper
• Cardboard
• Textbook
• Hand lens

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Transparent objects

• The windows on a school bus,
• A clear empty glass,
• A clear window pane,
• The lenses of some eyeglasses,
• Clear plastic wrap,
• The glass on a clock,
• A hand lens,
• Colored glass
• ALL of these are transparent. Yes, we can see
  through them because light passes through each of
  them.

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Translucent objects

• Thin tissue paper,
• Waxed paper,
• Tinted car windows,
• Frosted glass,
• Clouds,
• All of these materials are translucent and allow
  some light to pass but the light cannot be
  clearly seen through.

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Opaque objects

• Heavy weight paper,
• Cardboard
• Aluminum foil,
• Mirror, bricks, buildings,
• Your eyelids and hands,
• Solid wood door,
• All of these objects are opaque because light
  cannot pass through them at all.
• They cast a dark shadow.

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Warm Up

• 1. What happens when light is diffracted?
• 2. What happens when light is refracted?
• 3. Draw and label the EM spectrum.
• 4. What does it mean if something is translucent?
• 5. What is the law of reflection?

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Part 2 - Reflection

• Reflection from a mirror

Normal
Reflected ray
Incident ray
Angle of Reflection
Angle of Incidence
Mirror
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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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Clear vs. Diffuse Reflection

• Smooth, shiny surfaces have a clear reflection

Rough, dull surfaces have a diffuse
reflection. Diffuse reflection is when light is
scattered in different directions
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Refraction

• Light BENDS because it changes speed as it goes
  through different mediums. IE water

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Warm Up

• 1. Draw and label EM spectrum.
• 2. Give an example for each of the waves on the
  EM spectrum.

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Refraction
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Scattering

• Light is scattered by small particles and
  molecules in the atmosphere, the process is
  called scattering
• The color of the sky is the direct result of
  scattering of the sunlight. Rayleigh
• scattering

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Diffraction

• Diffraction is the slight bending of light as it
  passes around the edge of an object.

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• If the opening is much larger than the light's
  wavelength, the bending will be almost
  unnoticeable.
• However, if the two are closer in size or equal,
  the amount of bending is considerable, and easily
  seen with the naked eye.

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Draw
Red
Orange
White Light
Yellow
Green
Blue
Indigo
Violet
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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 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 because the higher the
frequency, the more it is refracted
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How do we see different colors?

• Black?
• Absorbs ALL the color energy frequencies of
  visible light
• White?
• Reflects ALL the color energy frequencies of
  visible light
• Grey?
• Absorbs and reflects percentages of all the
  colors
• Other colors?
• Reflects the color(s) you see and absorbs all
  others