Transcript Stop Faking It! Light

Light !!
It’s amazing!…Can you
imagine life without it?
Visible Spectrum
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Visible spectrum (visible light): a combination
of several different wavelengths of light
traveling together. It is part of the
Electromagnetic Spectrum.
Electromagnetic Spectrum
Electromagnetic waves are arranged by
the degree of frequency, from radio
waves to gamma waves.
 They are waves that don’t require a
medium (can travel through space)
 E-waves all travel at the speed of light
 The energy of the e-wave moves/ is
transferred by radiation
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Visible Spectrum
Visible Spectrum
Light is the electromagnetic wave that we
can see with our eyes
 ROYGBIV is the abbreviation for the color
spectrum
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How We See Light
Our eyes detect electromagnetic waves in
the visible light range that allows us to see
 Objects can be seen because they give off
light
 Their own light – luminous
 Reflected light – illuminated
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How We See Light…
Light reflecting off an object passes
through the lens of the eye stimulates
vision
 The retina in the eye senses wavelengths
of light as we perceive color
 Light waves will either pass through,
reflect or be absorbed by an object.
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What We See…
The color that we see is determined by
the wavelength reflected by the object
 If all colors are absorbed – We see black
 If all colors are reflected – We see white
 What ever color is reflected – that’s the
color we see.
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Important to know…
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Compare and contrast reflection and
refraction
Reflection
Refraction
Vocabulary
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Reflection: the bouncing of light from a
surface
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Refraction: the bending of light as it passes
through one material to another
Mirrors and Lenses
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Lenses refract
- bend light rays as
they pass through
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Mirrors reflect
Important to know…
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Look at how light as it passes through a
convex lens. How would you describe it?
A convex lens causes light to converge, or focus, producing
an image that is smaller than the original object.
Essential Knowledge, Skills, and
Processes
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Look at what happens to light as it passes
through a concave lens. How would you
describe it?
A concave lens causes light to diverge, or spread out,
producing a larger image than the original.
Mirrors: Plane, Concave & Convex
Plane Mirror Notes:
 Has a flat surface
 Image is right-side up
 Image is the same size
 Image is reversed left to right
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A virtual image is formed
Use – bathroom mirrors, other mirrors in the home
or in stores
Mirrors - Concave
Concave Mirror
Mirror curved inward
Image depends on optical axis, focal pt. focal length
Image depends on distance between object and mirror
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> than 1 focal length – upside down/real, reduced
< than 1 focal length – right-side up, virtual, enlarged
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Virtual and Real image
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Use – Car headlights, flash lights
Mirrors - Convex
Convex Mirror
 Mirror curved outward
 reflected rays don’t cross in front
 Extended behind mirror
 Shows virtual images right-side up
 Image is reduced (smaller)
 Use – Security in stores, side car mirrors
Lenses - Concave
Concave Lenses
 Thinner in the middle
 Light entering parallel to o. axis bend away from
each other
 Never forms a real image (always virtual)
 Virtual image is reduced (smaller than the
object)
 Use: Telescopes, microscopes, eye glasses
Lenses - Convex
Convex Lenses
 If object is < 1 focal length form the lens, a
virtual image is formed – and enlarged
 If object is > than 2 focal lengths from lens,
a real image is formed – and reduced
(smaller)
 Use: Magnifying lenses, Camera lens.
Some eye glasses
Mirrors and Lenses Compared
Plane Mirror – V , same size/ reversed
Concave Mirror V & E
R&R
Concave Lens V & R
Convex Mirror V & R
Convex Lens
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V – Virtual
E – Enlarged
R – Reduced
R & R – Real and Reduced
V&E
R&R
Important to know…
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Eyeglasses: have lenses to make
corrections
If you are nearsighted,
it’s hard to see
things that are far away.
If you are farsighted it’s
difficult to view nearby
objects
No correction needed
a. Normal eye
b. Myopia (nearsightedness)
c. Hyperopia (farsightedness)
Corrected with concave lens
Corrected with convex lens
Important to know…
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Explain the terms transparent, translucent,
and opaque, and give an example of each.
Plastic wrap
Wax paper
Transparent
Translucent
Aluminum Foil
Opaque
Interaction of Light with Objects
Transmit or transmission: the passing of
light through matter (air or objects).
 Transparent: materials that allow all light
to pass through – i.e., glass window, water
 Translucent: letting light through but
scattering it – i.e., wax paper
 Opaque: materials that do not let light
through - reflects - i.e., wood, metal
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Mixing Colors of Light vs. Mixing
Paints or Pigments
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Mixing Colors of Light
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In order to get white light, must combine all colors of
light
Red, blue and green are primary colors
When these combine they make secondary colors (cyan,
magenta and yellow)
Mixing Colors of Pigments
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Pigment is a material that gives a substance its color by
absorbing some, reflecting others
Primary pigment colors: yellow, cyan, and magenta
Mixing Colors of Light vs. Mixing
Paints or Pigments
Mixing Colors of Light
Mixing Colors of Pigments