Reflection and Refraction

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Reflection and Refraction

• TEKS 5.8B

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Objective 3 The student will demonstrate an
understanding of the physical sciences

• 5.8 The student knows that energy occurs in
  many forms
• (B) identify and demonstrate everyday examples of
  how light is reflected, such as from tinted
  windows, and refracted, such as in cameras,
  telescopes, and eyeglasses

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Every second of every day our eyes detect and
interpret rays of light whether that light is
coming from a natural source like the sun, or an
artificial source like a lamp. One of the
properties of light is that it travels in a
straight line, unless it is acted on by some
external force or condition.
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• However, sometimes our eyes can be fooled by the
  reflection and refraction of light. When
  interfered with, the path of light rays can be
  bounced or appear to be bent away from the
  original object making it seem larger or smaller
  than it really is.

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Reflection
When light strikes a surface and is redirected
back to its point of origin, this is reflection.
We can see objects when they reflect light, and
the reflected light enters our eyes. Most
objects reflect some of the light that hits
them. Smooth, shiny surfaces that absorb very
little light, will reflect light at almost the
same angle that the light hits it.
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Mirrors reflect images of objects because light
rays bounce off an object, travel in a straight
line to a mirror, bounce off the mirror, and then
travel to the eye of the observer.
Light beams
Mirror
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Refraction

• When the path of the light rays change directions
  and appear to bend we call it refraction.
• occurs when light passes from one substance to
  another of a different density(for example, from
  air to water)
• amount of refraction depends on the angle the
  light enters the new substance and the difference
  in the densities of the two
• the greater the angle, the more the light ray
  will be bent

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• Refracting telescopes and regular cameras use
  lenses to gather and focus light.
• Reflecting telescopes gather and focus light with
  mirrors. In a reflecting telescope, the observer
  sits inside the telescope, at the focal point of
  the reflected light.

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• Decide whether each object below best represents
  reflection or refraction. Click on your answer to
  find out if you are correct.

reflection
refraction
reflection
refraction
reflection
refraction
reflection
refraction
reflection
refraction
reflection
refraction
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• You are correct This picture illustrates
  reflection. Light bounces off of the object and
  does not pass through.

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• You are correct. This picture illustrates
  refraction. As light passes through the object
  it is bent by the denser substance.

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• Sorry, that is not correct

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• One way solid objects are classified is by how
  much light is allowed to pass through that
  object.
• A transparent object lets all of the light pass
  through.
• A translucent object lets some light pass
  through.
• An opaque object lets none of the light pass
  through.

opaque
transparent
translucent
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You are about to see several objects. Your job
is to decide if they are mostly transparent,
translucent or opaque -After you decide, click
on the object to see if you are correct. Some
pictures have two options.
The computer is opaque. No light is passing
through, so you cannot see anything behind it.
However, the screen is transparent. That is why
you can clearly see the mans face behind the
screen.
The brick wall is opaque. You cannot see any
part of the boy through the wall.
This sphere is transparent. You can clearly see
the man inside. The man, of course, is opaque.
These pens are translucent. Enough light passes
through to allow you to see some of the inside,
but not enough to see everything clearly.
This window is transparent. You can clearly see
the image on the other side because all of the
light is passing through.
This lampshade is translucent. Some of the light
passes through, but not all of it.
(NOTE The next picture will come in
automatically do not click again to advance.
Click only to check your answer.)
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Now, try answering these questions
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• Unless acted upon, how does light travel?
• Bent at a 500 angle.
• In a straight line.
• In a curved arch.
• Light doesnt have a preferred path.

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• Answer B is correct
• Light travels in a straight line.

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• These answers are not correct because
• Answer A Although light is often bent at a 500
  angle, that only happens when something acts upon
  it to make it change its path.
• Answer C Light does not usually travel in an
  arch.
• Answer D Light does have a preferred path a
  straight line.

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• All the following are examples of light being
  refracted EXCEPT

C
A
B
D
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• Answer choice D is correct. The mirror is using
  reflection to bounce light off of its surface.

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These answers are not correct because

• Answer A Look at the bent light rays. A rainbow
  is the result of light being refracted.
• Answer B Look at the bent light rays. A prism
  bends light.
• Answer C - The straw looks bent in this picture.
  It is an example of refraction, not reflection.

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• Which answer below names two conditions in which
  refraction can occur?
• Opaque and transparent
• Transparent and black
• Translucent and transparent
• Translucent and opaque

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Answer choice C is Correct

• In order for light to pass through an object and
  be refracted, the object must be transparent
  (see-through) or translucent (semi-transparent).

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These answers are not correct because

• Answer A - An opaque object would not allow light
  to pass through it.
• Answer B A black surface would not necessarily
  allow light to pass through it.
• Answer D An opaque surface would not allow
  light to pass through it.

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• In this picture, the straw appears to be bent.
  This is because
• milk is an opaque substance.
• light is being refracted.
• it is a magic trick.
• light is being reflected.

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Answer B is correct.

• The straw appears to be bent because light is
  being refracted as it passes through the air into
  the liquid.

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These answers are not correct because

1. An opaque substance if the liquid were opaque,
   we would not be able to see the straw.
2. A magic trick it is not a trick that the light
   is being bent, or refracted, as it moved through
   the liquid
3. Light being reflected although some light may
   be reflected by the glass, that is not the reason
   why the straw appears to be bent.

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• Which of these objects best illustrates
  reflection?
• Prism B. Rose Quartz
• C. Window D. Paper

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Answer C is correct.

• The smooth surface of the window is reflecting
  the image of nearby buildings.

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These answers are not correct because

• A Prism light is being refracted as it passes
  through the prism
• B - Rose Quartz the surface of this rock is too
  rough to reflect light
• D -Paper since paper is opaque, light would not
  bounce off or be refracted.

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Look at the objects below. Which one uses
refraction?
A
B
C
D
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• Answer Choice C is CORRECT.
• A rainbow uses refraction. The light is bent as
  it passes through the air and water droplets.

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Answer choice A, B, and D are not correct.
Mirrors use reflection of light in order to see
an object, not refraction.
The End
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Resources for images

• Transparent screen
• www.computeramerica.com/.../2005/2005-04-04.htm
• Transparent watch
• www.swatchforum.com/curiosities.html
• Virtusphere
• www.virtusphere.net/product.htm
• Opaque pitchers
• www.guild.com/artitem/30336.html
• Transclucent pen
• www.promotional-pens.us/promotional-pens/basi...