Applications of Lenses and Mirrors

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Applications of Lenses and Mirrors
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Combinations of Lenses
Image of 1st lens calculated as though the 2nd
lens were not present.
Image formed by 1st lens is treated as the object
for the 2nd lens.
Object in front of lens real (do) Object
behind lens virtual (do -)
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20.0 cm
30.0 cm
f2 20.0 cm
f1 10.0 cm
Lens 1
di
15 cm
m
-1/2
Lens 2
di
m
- 6.7 cm
4/3
Virtual image 6.7 cm to left of L2 M -2/3
(inverted)
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30.0 cm
10.0 cm
f2 20.0 cm
f1 10.0 cm
Lens 1 di 15 cm m - 1/2
Lens 2
m
4 cm
di
4/5
Real image 4 cm to right of L2 M -2/5
(inverted)
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If the 2 lenses are put back-to-back to form a
single lens, what is f?
L1 d0 8, di
10.0 cm
L2 d0 -10.0 di
0.067 cm
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1. 30 cm c) 10 cm, inverted

d) 16.7 cm
e) M -2/3
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Type of image Type of lens
real
converging
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Focusing
adjust position of lens to put image on film
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Aperture
similar to iris
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Film Projector
Type of image produced
enlarged, real
converging
Type of lens used
slightly beyond F
Position of object
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Motion Pictures
Persistence of Vision
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Duplicating (Xerox) Machine

• Copy is a

real
image of original
Type of lens
Converging
For same size image, object located
_at_ 2F
For enlargement, object located
bet. F 2F
For reduction, object located
beyond 2F
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Magnifying Lens
Magnifying Lens
enlarged, virtual
Type of image
Type of lens
Converging
Position of object
just inside F
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Telescope
Objective lens forms a real image of the object.
The eyepiece lens forms an enlarged virtual
image of the real image.
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Compound Microscope
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Spherical Aberration
When mirror (or lens) is spherical in shape,
rays which reflect off edges converge too
quickly. Results in a blurry image.
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SOLUTION
Mirror make mirror parabolic in shape
Lens Use a circular stop (diaphragm) in front
of lens
If block a portion of the lens, image becomes
dimmer.
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Chromatic Aberration
Dispersion of light into colors produces
convergence at different points and a blurry
image.
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SOLUTION (for lens)
Achromatic lens is a combination converging and
diverging lens. Cancels effect of dispersion.
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Correction for chromatic aberration in mirrors?
No dispersion for mirrors