Spherically Curved Mirrors

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Spherically Curved Mirrors

• Distort, Magnify, Focus

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Mirrors can be curved in a circle (spherical) or
deep curve (parabolic).Which is better? A.
spherical B. parabolic
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• Parabolic is sharper(no shape aberrations)

• Spherical is cheaper
• easier to model
• but cant focus as well outside rays

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light rays from the sun all converge ata.
radius of curvature C b. vertex Ac. focal
pt F. d. between C F
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Curved Mirror Terms
Note f C/2 or R/2
Focal point
Principal axis
C
f
Vertex
Center of curvature
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Which is a converging mirror?A. left B. right
C. both
Security mirror
Parabolic Radio wave telescope
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Which of these is convex?A. left B. right C.
neither!
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Mirror Vocabulary
Converging Light rays come together at a point
Concave mirror A converging mirror where light
is reflected from an inner curved
surface--dented in
Diverging Light rays spread out do not come
together
Convex A diverging mirror where light is
reflected from an outer curved surface--bulging
out
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Mirror Vocabulary
Real Image Light rays really converge at a
point can be __________on a screen
Real Image
Object

• Virtual Image
• Light rays ____________ at a point can not be
  projected at a screen

Virtual Image
Object
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Flat mirrors have only virtual images, just like
which mirror?A. concave B. Convex.C. Both
d. neither
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Spherical Mirrors

• Convex mirrors virtual images only

Note Rays 1,2, and 3 are called principle rays.
See your text.
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What type of images can you get out of a concave
mirror?A. real B. virtual C. both D. neither
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Spherical Mirrors

• Concave mirrors real and virtual images

Virtual if object placed closer than the focal
point
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Convexsummary

• (outside of spoon)
• Diverges light
• Forms only _virtual_______, small images
• car side-mirrors(objects appear further since
  they also appear smaller! Watch out for t-rex)
• security mirrors- small upright images so can
  identify everyone all on the same mirror

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Concavesummary

• (inside of spoon)
• if object not too close (not past _focal_____
  point)
• Real, inverted images converging light
• Size may be large or small
• Projectors, digital TV, satellite, large
  telescopes
• if object too close (past focal point)
• virtual, __large_______ images diverging light
• Size always enlarged
• Make-up mirrors, eyepiece of telescopes

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Too close, at focal pt., too far
3 different places to place an object for a
concave mirror
3 different imagesLarge Virtual, no image, real
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And get the same resultAll images are small,
virtual, upright
You can put an object in front of a convex mirror
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Principal Rays- image is everything!
Locate the image using at least 2 principal rays-
find where the reflected rays cross
Object
Ray 1
C
f
Image
Ray 3
Ray 2
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Principal Ray 1 parallel/focus
Ray 1 parallel ray Any light ray parallel to
the principal axis will be reflected through the
focal point
C
f
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Principal Ray 2 focus/parallel
Ray 2 focus ray Any light ray passing through
the focus will be reflected parallel to the
principal axis
C
f
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Principal Ray 3- center/return
Ray 3 center ray Any light ray striking the
center at any angle will be reflected back onto
______ at the same angle
C
f
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Concave mirror has 5 regions for placing an
object. Which produces no images?A. 1 b.
2 c. 3 d. 4 e. 5
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Object at case 4 (at focal pt)produces a beam of
light(not a focus image)

• Guess where your cars light bulb is placed?

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Concave mirror has 5 regions for placing an
object. Which produces only virtual images?A.
1 b. 2 c. 3 d. 4 e. 5
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Objects closer than focal pt. in front of concave
mirrors make virtual images!- see them, but
cant touch or be burned by
Large, virtual, upright image if too close to a
concave mirror!
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Concave mirror has 5 regions for placing an
object. Which produces only real images?A. 1
b. 2 c. 3 d. 4 e. 5
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Real images for cases 1-3case 1 small, case 2
same case 3. big
Real, upright images if further than focal length
of concave
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Concave mirror closer the object, the bigger
the image gets!
But closer than F, the rays cant be focused for
real images!
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convex mirrors what type of images do they
make? a. Only real b. only virtual c. both
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All images are small, virtual, upright
convex mirrors diverge light and only make
virtual images! (closer you get, the image gets a
little bigger but always reduced)
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Review problem match the objects and
images (use only the up arrows as objects for
less headache!)
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Object 1 --------image 5 (real, reduced,
inverted)Object 2-------- image 4 (real,
enlarged, inverted)Object 5---------no image!
Should be 3 but upside down
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The Image Equation(Locating Images with Ease)
Object
f
do
C
di
Image
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Magnification(Locating Images with Ease)
Where hi height of _image_____ ho height of
_object di distance to image from mirror do
distance to object from mirror
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Sign Conventions for Mirror Equations
f for concave - for convex____
f 5 cm
f -5 cm
di for real image, - for virtual
image
Real Image
Object
Object
Virtual Image
di 15 cm
di - 12 cm
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Math proof geometry!
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Spherical Mirrors( is in a general sense for
real or normal results)