Agenda
• Examine Light• 32.1-32.3
– Qualitative For most part– Light traveling in materials– Existence of E&B fields in light
• 33– Reflection&refraction– Polarization– Dispersion
• Finish by Monday at latest– Explore polarization in lab Tues
Light Meets Matter
Metal?
Ray of LightThink Beam
What Happens?
Metals absorb E-fieldsNo light enters metalSome absorbedSome reflected
I < I0
Light Meets Matter
Non-Metal?
Ray of LightThink Beam
What Happens?
Some entersSome reflectsSome gets absorbedAffects speed by polarization
Reflected + Refracted Intensity < Original
Magic of Trigonometry
• Reflection
• Incident Angle = Reflected Angle
• Measure from Surface Normal
ReflectiveSurface
R
First Thought
• Why are Mirrors Blurry after a shower?
ReflectiveSurface
R
Reflection off flat surface
First Thought
• Why are Mirrors Blurry after a shower?
ReflectiveSurface
R
Reflection off water droplet…
Where does light come from?
• Feet?
Mirror
Light
Light reflected/emitted from feetAll different anglesOnly one angle bounces off mirror right
Where does light come from?
• Feet?
Mirror
Light
Light reflected/emitted from feetAll different anglesOnly one angle bounces off mirror rightIncident Angle Must Equal Reflected!
Let’s Try a half Height Mirror
• Say you are 6’ Tall, Mirror 3’ Tall, Mirror 5’ Away• How much of yourself can you see?
What is light ray for bottom part?
Let’s Try a half Height Mirror
• Say you are 6’ Tall, Mirror 3’ Tall, Mirror 5’ Away• How much of yourself can you see?
Where does ray come from?
Let’s Try a half Height Mirror
• Say you are 6’ Tall, Mirror 3’ Tall, Mirror 5’ Away• How much of yourself can you see?
Where does ray come from?Find angle…
Let’s Try a half Height Mirror
• Say you are 6’ Tall, Mirror 3’ Tall, Mirror 5’ Away• How much of yourself can you see?
Where does ray come from?Find angle…
Let’s Try a half Height Mirror
• Say you are 6’ Tall, Mirror 3’ Tall, Mirror 5’ Away• How much of yourself can you see?
Where does ray come from?Find angle…tan()=(3/5)
3
5
Let’s Try a half Height Mirror
• Say you are 6’ Tall, Mirror 3’ Tall, Mirror 5’ Away• How much of yourself can you see?
Where does ray come from?Find angle…tan()=(3/5)Where does light come from?
3
5
Let’s Try a half Height Mirror
• Say you are 6’ Tall, Mirror 3’ Tall, Mirror 5’ Away• How much of yourself can you see?
Where does ray come from?Find angle…tan()=(3/5)=tan(R)
3
5
R
Does it Matter How far Away Mirror is?
• Think: Total angle is 2x incident angle
• If mirror is ½ height….– Light at edge travels ½ vertical each way– So makes up 2x height
• Can prove mathematically
• Or just calculate at different distances
• Or look in mirror….