lecture 17 ray optics-3 chapter 23 physics 270 dennis papadopoulos march 22, 2010
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Lecture 17Ray Optics-3 Chapter 23
PHYSICS 270Dennis Papadopoulos
March 22, 2010
Total Internal Reflection
Image by Refraction
1 1 2
2 2 1
1 2
tan sin
tan sin
, 1
s s s s
for
€
l = stanθ1 = s' tanθ2
EXAMPLE 23.13 A goldfish in a bowl
What is a lens?Device that provides a capability to create bright and well focused images. How?
Use Refraction to create images out of divergent light rays
• Focal point
• Focal length
• Property of lens no matter how it is used
• Distance from lens that paraxial rays converge
• Reversibility
Converging and Diverging Lenses
Thin Lenses – Real Image –Special Rays
Thin lens-> d<<f,s,s’
€
1
s+
1
s'=
1
f Inverted Image
Thin Lenses: Ray Tracing
Tactics: Ray tracing for a converging lens
Tactics: Ray tracing for a converging lens
Lateral MagnificationThe image can be either larger or smaller than the object, depending on the location and focal length of the lens. The lateral magnification m is defined as
1. A positive value of m indicates that the image is upright relative to the object. A negative value of m indicates that the image is inverted relative to the object.
2. The absolute value of m gives the size ratio of the image and object: h'/h = |m| .
s>f h’/h=s’/s
Virtual Image
s’<0 m>0 image upright
EXAMPLE 23.10 Magnifying a flower
s<f
Diverging Lenses
Thicker at the edges
Demagnification
Diverging lenses Ray Tracing