UNIT 8 Light and Optics

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# UNIT 8 Light and Optics - PowerPoint PPT Presentation

UNIT 8 Light and Optics. mirror. 3. O. 1. 2. S. 4. ConcepTest 35.2a Mirror I. An observer at point O is facing a mirror and observes a light source S . Where does the observer perceive the mirror image of the source to be located?. mirror. 3. O. 1. 2. S. 4.

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Presentation Transcript

mirror

3

O

1

2

S

4

ConcepTest 35.2a Mirror I

An observer at point O is facing a mirror and observes a light source S. Where does the observer perceive the mirror image of the source to be located?

mirror

3

O

1

2

S

4

ConcepTest 35.2a Mirror I

An observer at point O is facing a mirror and observes a light source S. Where does the observer perceive the mirror image of the source to be located?

Trace the light rays from the object to the mirror to the eye. Since the brain assumes that light travels in a straight line, simply extend the rays back behind the mirror to locate the image.

Follow-up: What happens when the observer starts moving

toward the mirror?

### Wednesday February 15th

Light and Optics

Wednesday, February 15

TODAY’S AGENDA

• Flat Mirrors

UPCOMING…

• Thurs: Curved Mirrors Concave
• Fri: NO School
• Mon: Curved Mirrors Convex
• Tue: Problem Quiz #1
• Color and Polarization

Chapter 13

Light and Reflection

The Ray Model of Light

Light very often travels in straight lines. We represent light using rays, which are straight lines emanating from an object. This is an idealization, but is very useful for geometric optics.

Reflection; Image Formation by a Plane Mirror

Law of reflection: the angle of reflection (that the ray makes with the normal to a surface) equals the angle of incidence.

Reflection; Image Formation by a Plane Mirror

When light reflects from a rough surface, the law of reflection still holds, but the angle of incidence varies. This is called diffuse reflection.

Reflection; Image Formation by a Plane Mirror

With diffuse reflection, your eye sees reflected light at all angles. With specular reflection (from a mirror), your eye must be in the correct position.

Reflection; Image Formation by a Plane Mirror

What you see when you look into a plane (flat) mirror is an image, which appears to be behind the mirror.

This is called a virtual image, as the light does not go through it. The distance of the image from the mirror is equal to the distance of the object from the mirror.

Reflection; Image Formation by a Plane Mirror

Image

Image in a Plane Mirror

Mirror

Object

Reflection; Image Formation by a Plane Mirror

f

q

h

Image

q

f

di

Image in a Plane Mirror

Mirror

Object

do

The image is as far behind the mirror as the object is in front of the mirror.

The mirror needs to be only half your height!

Reflection; Image Formation by a Plane Mirror

di

Similar Triangles

Image

hi

q

f

f

Image in a Plane Mirror

Mirror

do

Object

ho

=

Image is the same size as the object.