Download Chapter 18 Mirrors and Lenses

Chapter 18
Mirrors and Lenses
18.2 Lenses
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A.
B.
C.
D.
Types of Lenses
Convex Lenses
Concave Lenses
Optical Instruments that Use Lenses
A. Types of Lenses
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1. A lens is made of transparent material with a
refractive index larger than air.
2. Each face of the lens is part of a sphere and
can be convex, concave, or flat.
3. A convex lens is thicker in the middle than at
the edges and are converging lenses.
4. A concave lens is thinner in the middle and is
a diverging lens.
B. Convex Lenses
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1. The thin lens model.
2. Real Images from Convex Lenses.
3. Lens/Mirror Equation conventions
a. f is positive for convex lenses
 b. f is negative for concave lenses
 c. do is positive on the object side of the lens
 d. di is positive on the other side of the lens
 e. di is negative on the object side of the lens where
images are virtual.
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4. Why use a larger lens?
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More light gathering ability
Virtual images
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Images formed when the object is inside the focal
point.
C. Concave Lenses
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Images formed by concave lenses are virtual,
erect, and reduced in size no matter how far
from the lens the object is placed.
Defects in lenses.
Spherical aberration
 Chromatic aberration
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Achromatic lens
D. Optical Instruments that use
Lenses
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Nearsighted or myopic eyes
Farsighted or hyperopia eyes
Astigmatism
Contact Lenses
Microscopes
Telescopes