Light: Geometric Optics

Chapter 23

23-1 Ray Model of Light

• Light travels in a straight line so a ray model is used to show what is happening to the light

• This model assumes light to travel in a straight line and is represented by narrow lines called light rays

23-2 Reflection from a Plane Mirror

The Angle of reflection equals the angle of incidence

Diffuse reflection

When light is incident upon a rough surface, microscopically rough

Image

• The image is what is seen in the mirror

• Virtual image

• Real image

23-3 Formation of Images by Spherical Mirrors

• Convex – reflects from the outside of the sphere, rearview mirrors

• Concave – reflects from the inside of the sphere, cosmetic mirrors

Focal Point & Focal Length

Image Formation-Ray Diagrams

Mirror Equation & Magnification

Mirror Equation

• Where• do is the object distance• di is the image distance• f is the focal length

io ddf

111

Magnification Equation

• Where• m is the magnification • ho is the object height• hi is the image height• do is the object distance• di is the image distance

o

i

o

i

d

d

h

hm

• Sign gives the correct location and orientations of the image

• If hi + then upright, - inverted

• If di or do + then in front of mirror, - behind mirror

Objects closer to concave mirror

Convex Mirror• Focal point behind the mirror

• Focal length is negative