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Flat Lens (Window)
n1n2
Incident ray is displaced, but its direction is not changed.
t
1
1
If 1 is not large, and if t is small, the displacement, d, will be quite small.
d
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Converging LensAll rays parallel to principal axis pass through focal point F. Double Convex
P.A.
F
A beacon in a lighthouse produces a parallel beam of light. The beacon consists of a bulb and a converging lens. Where should the bulb be placed?
nlens > noutside
F
• At F
• Inside F
• Outside F
P.A.
F
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Converging LensAll rays parallel to principal axis pass through focal point F. Double Convex
P.A.
F
A beacon in a lighthouse produces a parallel beam of light. The beacon consists of a bulb and a converging lens. Where should the bulb be placed?
nlens > noutside
F
• At F
• Inside F
• Outside F
P.A.
F
F
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1) Rays parallel to principal axis pass through focal point.2) Rays through center of lens are not refracted.
3) Rays through F emerge parallel to principal axis.
Converging Lens Principal Rays
F
F
Object
P.A.
Image is (in this case): Real or Imaginary
Inverted or Upright
Enlarged or Reduced
![Page 5: Flat Lens (Window) n1n1 n2n2 Incident ray is displaced, but its direction is not changed. tt 11 11 If 1 is not large, and if t is small, the](https://reader036.vdocuments.mx/reader036/viewer/2022062518/56649cd85503460f949a04e6/html5/thumbnails/5.jpg)
1) Rays parallel to principal axis pass through focal point.2) Rays through center of lens are not refracted.
3) Rays through F emerge parallel to principal axis.
Converging Lens Principal Rays
F
F
Object
P.A.
Image is: real, inverted and enlarged (in this case).
Image
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1) Rays parallel to principal axis pass through focal point.2) Rays through center of lens are not refracted.
3) Rays toward F emerge parallel to principal axis.
Diverging Lens Principal Rays
F
F
Object
P.A.
Image is (always true): Real or Imaginary
Upright or Inverted
Reduced or Enlarged
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1) Rays parallel to principal axis pass through focal point.2) Rays through center of lens are not refracted.
3) Rays toward F emerge parallel to principal axis.
Diverging Lens Principal Rays
F
F
Object
P.A.
Image is virtual, upright and reduced.
Image
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CONVEX LENS, OBJECT BEYOND 2F
From the above diagram you can see that the image is (circle the correct choices):
ENLARGED, SAME SIZE, or REDUCED
INVERTED or ERECT
REAL or VIRTUAL
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CONVEX LENS, OBJECT BEYOND 2F
From the above diagram you can see that the image is (circle the correct choices):
ENLARGED, SAME SIZE, or REDUCED
INVERTED or ERECT
REAL or VIRTUAL
This could be used in a camera. Big object on small film
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CONVEX LENS, OBJECT AT 2F
From the above diagram you can see that the image is (circle the correct choices):
ENLARGED, SAME SIZE, or REDUCED
INVERTED or ERECT
REAL or VIRTUAL
![Page 11: Flat Lens (Window) n1n1 n2n2 Incident ray is displaced, but its direction is not changed. tt 11 11 If 1 is not large, and if t is small, the](https://reader036.vdocuments.mx/reader036/viewer/2022062518/56649cd85503460f949a04e6/html5/thumbnails/11.jpg)
CONVEX LENS, OBJECT AT 2F
From the above diagram you can see that the image is (circle the correct choices):
ENLARGED, SAME SIZE, or REDUCED
INVERTED or ERECT
REAL or VIRTUAL
![Page 12: Flat Lens (Window) n1n1 n2n2 Incident ray is displaced, but its direction is not changed. tt 11 11 If 1 is not large, and if t is small, the](https://reader036.vdocuments.mx/reader036/viewer/2022062518/56649cd85503460f949a04e6/html5/thumbnails/12.jpg)
CONVEX LENS, OBJECT BETWEEN F AND 2F
From the above diagram you can see that the image is (circle the correct choices):
ENLARGED, SAME SIZE, or REDUCED
INVERTED or ERECT
REAL or VIRTUAL
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CONVEX LENS, OBJECT BETWEEN F AND 2F
From the above diagram you can see that the image is (circle the correct choices):
ENLARGED, SAME SIZE, or REDUCED
INVERTED or ERECT
REAL or VIRTUAL
This could be used as a projector. Small slide on big screen
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CONVEX LENS, OBJECT AT F
From the above diagram you can see that the image is (circle the correct choices):
ENLARGED, SAME SIZE, or REDUCED
INVERTED or ERECT
REAL or VIRTUAL
![Page 15: Flat Lens (Window) n1n1 n2n2 Incident ray is displaced, but its direction is not changed. tt 11 11 If 1 is not large, and if t is small, the](https://reader036.vdocuments.mx/reader036/viewer/2022062518/56649cd85503460f949a04e6/html5/thumbnails/15.jpg)
CONVEX LENS, OBJECT AT F
From the above diagram you can see that the image is (circle the correct choices):
NO IMAGE
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CONVEX LENS, OBJECT BETWEEN F AND LENS
From the above diagram you can see that the image is (circle the correct choices):
ENLARGED, SAME SIZE, or REDUCED
INVERTED or ERECT
REAL or VIRTUAL
![Page 17: Flat Lens (Window) n1n1 n2n2 Incident ray is displaced, but its direction is not changed. tt 11 11 If 1 is not large, and if t is small, the](https://reader036.vdocuments.mx/reader036/viewer/2022062518/56649cd85503460f949a04e6/html5/thumbnails/17.jpg)
CONVEX LENS, OBJECT BETWEEN F AND LENS
From the above diagram you can see that the image is (circle the correct choices):
ENLARGED, SAME SIZE, or REDUCED
INVERTED or ERECT
REAL or VIRTUAL
This is a magnifying glass
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CONCAVE LENS
From the above diagram you can see that the image is (circle the correct choices):
ENLARGED, SAME SIZE, or REDUCED
INVERTED or ERECT
REAL or VIRTUAL
![Page 19: Flat Lens (Window) n1n1 n2n2 Incident ray is displaced, but its direction is not changed. tt 11 11 If 1 is not large, and if t is small, the](https://reader036.vdocuments.mx/reader036/viewer/2022062518/56649cd85503460f949a04e6/html5/thumbnails/19.jpg)
CONVEX LENS, OBJECT BETWEEN F AND LENS
From the above diagram you can see that the image is (circle the correct choices):
ENLARGED, SAME SIZE, or REDUCED
INVERTED or ERECT
REAL or VIRTUAL
![Page 20: Flat Lens (Window) n1n1 n2n2 Incident ray is displaced, but its direction is not changed. tt 11 11 If 1 is not large, and if t is small, the](https://reader036.vdocuments.mx/reader036/viewer/2022062518/56649cd85503460f949a04e6/html5/thumbnails/20.jpg)
Converging LensWhich way should you move object so image
is real and diminished?
(1) Closer to lens(2) Further from lens(3) Converging lens can’t create real
diminished image.
F
F
Object
P.A.
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Converging LensWhich way should you move object so image
is real and diminished?
(1) Closer to lens(2) Further from lens(3) Converging lens can’t create real
diminished image.
F
F
Object
P.A.
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Which way should you move object so image is real?
1) Closer to lens
2) Further from lens
3) Diverging lens can’t create real image.
ACT: Diverging Lenses
F
F
Object
P.A.
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Which way should you move object so image is real?
1) Closer to lens
2) Further from lens
3) Diverging lens can’t create real image.
ACT: Diverging Lenses
F
F
Object
P.A.
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P.A.
F
Focal point determined by geometry and Snell’s Law: n1 sin() = n2 sin()
Fat in middle = ConvergingThin in middle = DivergingLarger n2/n1 = more bending, shorter focal length.n1 = n2 => No Bending, f = infinityLens in water has _________ focal length!
n1<n2
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P.A.
F
Focal point determined by geometry and Snell’s Law: n1 sin() = n2 sin()
Fat in middle = ConvergingThin in middle = DivergingLarger n2/n1 = more bending, shorter focal length.n1 = n2 => No Bending, f = infinityLens in water has larger focal length!
n1<n2
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1) Rays parallel to principal axis pass through focal point.2) Rays through center of lens are not refracted.
3) Rays through F emerge parallel to principal axis.
Assumptions: • monochromatic light incident on a thin lens.
• rays are all “near” the principal axis.
Converging Lens Principal Rays
F
F
Object
P.A.
Image is real, inverted and enlarged
Image
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Preflight 19.1A converging lens is used to project a real image
onto a screen. A piece of black tape is then placed over the upper half of the lens.
How much of the image appears on the screen?
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Java
A converging lens is used to project a real image onto a screen. A piece of black tape is then placed over the upper half of the lens.
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Still see entire image (but dimmer)!
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Lens Equation
cm 1011
cm 151
id
F
F
Object
P.A.
do
di
f
Image
1do
1di
1f
• do = distance object is from lens:
• Positive: object __________ lens
• Negative: object __________ lens
• di = distance image is from lens:
• Positive: ________ image (behind lens)
• Negative: ________ image (in front of lens)
• f = focal length lens:• Positive: ___________ lens
• Negative: ___________ lens
di =
m =
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Lens Equation
cm 1011
cm 151
id
cm 30id
o
i
dd
m 2
F
F
Object
P.A.
do
di
f
Image
1do
1di
1f
• do = distance object is from lens:
• Positive: object in front of lens
• Negative: object behind lens
• di = distance image is from lens:
• Positive: real image (behind lens)
• Negative: virtual image (in front of lens)
• f = focal length lens:• Positive: converging lens
• Negative: diverging lens
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Multiple LensesImage from lens 1 becomes object for lens 2 1
f1 f2
2
Complete the Rays!!
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Multiple Lenses: Magnification
f1 f2
do = 15 cm
f1 = 10 cm
di = 30 cm
f2 = 5 cm
L = 42 cm
do=12 cm
di = 8.6 cm
1m
2m 21mmmnet
1 2
Net magnification:mnet = m1 m2