THE WONDER OF REACTION

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Lecture 17, Chapter 26 28Reflection
Refraction
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Electromagnetic Waves (Ch 26)
Visible light is one type of electromagnetic
wave. Is light a A. transverse or B. longitudinal
wave?
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Electromagnetic wave spectrum
Recall v 3 x 108 m/s, and
v ?f
Know the different types of electromagnetic waves!
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Properties of LightTypes of Reflection (Ch 28)
What are some examples of each of these?
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Law of Reflection
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Reflection law practice
At what angle to the normal does light hit the
second mirror?
Compare the direction of the first ray to that
reflected from the second mirror.
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Image in a plane mirror
Use the Law of Reflection to find the location
and height of the image in a plane mirror.
What are real and virtual images?
Is the image a real image or a virtual image?
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Images in curved mirrors
The Law of Reflection is used to figure out where
the rays go.
Are the images real or virtual?
What would happen if the man using the right
mirror was further away from the mirror?
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Reflection in rear projection TVs
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Refraction
Why do the wheels change direction when they hit
the grass?
Refraction is the bending of waves as they pass
obliquely from one medium into another
due to a change of wave speed (density).
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Laws of Refraction
1. When going from a less dense to a more dense
medium, the refracted ray bends toward the
normal. 2. Light can go either way along the
ray! 3. When going from a more dense to a less
dense medium, the refracted ray bends away from
the normal.
4. If incidence angle is zero then there is
no bending.
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Refraction Practice

• Follow the ray from Q to the persons eye.
• Apply the rules of refraction to this situation.
• Note that, because of refraction, the bottom of
  the pool or anything underwater seems closer than
  it really is.

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Mirage
Light travels faster in warmer, less dense air
near the ground, so it is refracted upward toward
the cooler more dense air. The line of sight
gives the impression of the tree upside downa
mirage!
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How does a Prism work?
Different colors refract or bend differently.
This fanning out of colors by refraction is
known as dispersion.
Which color is bent the most? Can you figure out
where all the rays come from?
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Total Internal Reflection
Used in binoculars, fiber optic cables,
endoscopic probes, laser surgery, and many other
modern optical applications.
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Fiber Optics
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Endoscopy
Endoscopes use a bundle of optical fibers to
transmit an image out of the body.
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I am putting my bow in the clouds. It will be
the sign of my covenant with the world to you
and all the animals that a flood will never again
destroy all living beings. ?Gen. 913-15
Dispersion of colors by raindrops. The spherical
rain drop acts like a prism. Different colors
are refracted at different angles due to
dispersion of light at the raindrop. Is the
rainbow you see out in the sky or in your eyes?
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• It occurs because of Refraction and Reflection
• Two refractions - entering and leaving the
  raindrop
• One reflection - at the back of raindrop
• Red is seen on top because it bends the least.
• The color red leaving the raindrop makes an angle
  of 42.2o with sun light entering the raindrop.
  The color violet leaving the raindrop makes an
  angle of 40.6o with sun light entering the
  raindrop.

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Lens Function Types
Converging Diverging
Lenses work because of the refraction of light at
the two surfaces
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Lens Refraction converging
Parallel rays are brought to a focal point F by a
converging lens.
Rays from a point of light located at the focal
point F are sent out parallel by the converging
lens.
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Lens Refraction diverging
Parallel rays of light diverge from the focal
point of a diverging lens.
Rays of light heading toward a focal point of the
diverging lens are sent out parallel.
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Principal Rays for a Thin Lens

• A ray parallel to the lens axis then through 2nd
  focal pt.
• A ray straight through the vertex.
• A ray through the 1st focal point and then
  parallel.

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The Lens Equation
f
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Lens Example

• Imagine that you have a lens with a focal length
  of 10 cm.
• A. Sketch a ray diagram for the lens using the
  line below.
• B. If the object is 30 cm away calculate the
  image location?

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How do a camera the eye work?
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Structure of the eye
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Insect eye with many lenses
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God is Worth Worshiping
As a light ray leaving a less dense medium bends
toward the normal, So a
person leaving the emptiness of the world bends
toward Christs life. OH Worship God
whose perfection is
seen in the life of Jesus!