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