Mirrors

Plane and Spherical

Plane Mirrors• Flat mirrors. Which type of image?

Virtual

We perceive the image at

point I where the ray

extensions intersect

Clifton Bluhm

Real Penny

Image of Penny

http://www.throwlikeagirl.net/archives/000040.html

http://www.waitingtimetoys.com/wallmodels.2/fun.mirror.html

Curved MirrorsCurved Mirrors

Curved Curved ReflectorsReflectors

Principle AxisPrinciple Axis

FocalFocalPointPoint

FocalFocalLength Length

(cm)(cm)

http://www.atnf.csiro.au/news/press/images/urumqi/urumqi_25m_telescope.jpg

http://www.windows.ucar.edu/earth/images/arecibo.jpg

Diameter = 305 m (1000 ft) Built = 1963Location = Puerto Rico

Arecibo Radio Telescope

Focal Length of a Spherical Mirror

2

Rf

R – Radius of Curvature

Ray Tracing

We will predict the image that will be formed

by a mirror or lens using ray tracing. We

typically care about three ‘special’ rays:

1. Two rays that go through the focal points

2. The ray that go through the center of the object

Spherical Mirrors and Ray Tracing

The focal point of a concave mirror

The focal point of a convex mirror

Slide 18-32

Three Sets of Special Rays for a Concave Mirror

Slide 18-33

A Real Image Formed by a Concave Mirror

Slide 18-34

Slide 18-35

Three Sets of Special Rays for a Convex Mirror

Slide 18-36

Ray Tracing for a Convex Mirror

Slide 18-37

Images and Mirrors

• Real images will form on the side of the mirror where the object is located

• Virtual images will form on the opposite side

The Thin-Lens Equation – This works for both mirrors and lenses

1

s

1

s

1

fThin-lens equation (also works for mirrors)

relating object and image distance to focal length

Slide 19-10

Sign Conventions for Lenses and Mirrors

Slide 19-11

Magnification

m hh

ss

Slide 18-26

A random place for this slide but it needs to go somewhere. The next slide shows the different values from this equation.

Ray Tracing: Virtual Images

Slide 18-27

Sample ProblemA convex mirror has a focal length of -10

cm. An object of 4 cm high is placed 20 cm

in front of the mirror.

1. Find the position and size of the image.

2. Describe the nature of the image.