Transcript Converging and Diverging Lenses

Refraction of Light
EM lesson 8
do
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Thicker in the center than at the edges
Have positive focal lengths
Converge parallel rays of light that pass
through them
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If an object is beyond C, the image is real,
inverted, and smaller
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If the object is at C (or 2F), the image is real,
inverted, and the same size as the object
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If the object is between C and F, the image is
real, inverted, and enlarged.
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If the object is at F, no image is formed
1
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f
1

do
1
1 0 .0 cm
1
di
1
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
3 0 .0 cm
1
di
0 .1 0 0 / cm  0 .0 3 3 3 / cm 
1
di
0 .0 6 6 7 / cm 
1
di
d i  1 5 .0 cm
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A virtual image is formed if the object is
located between the focus and the lens.
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if object is between F and the lens, image
formed is virtual, upright and larger
F
F
1
f

1
do

1
1
di
8.00 cm
1

6.00 cm
0.125 / cm  0.1667 / cm 
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1
di
1
di
 0.0416667 / cm 
1
di
d i   24.0 cm ( the negative m eans it is virtual )
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Thinner at the center than the edges
Have negative focal lengths and diverge
parallel rays of light passing through them
• The focal length depends on the index of
refraction and curvature
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As n (index of refraction) increases, focal
distance decreases
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As curvature increases, focal distance
decreases also
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concave lens will only produce a virtual image
F
• Image formed is virtual upright and smaller
than original object
1
f

1
do
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1
1
di
 5.00 cm
1
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 0.200 / cm  0.100 / cm 
10.0 cm

1
di
1
di
 0.300 / cm 
1
di
d i   3.33 cm ( the negative m eans it is virtual )
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to tell whether an object is real or virtual, erect or
inverted, enlarged or diminished – DO THE MATH
Real image – di > 0
Virtual image – di < 0
Erect image – hi > 0
Inverted image – hi < 0
Enlarged image – M > 1
Diminished image – M < 1