Physics 1230: Light and Color Ivan I. Smalyukh, Instructor Office: Gamow Tower, F Phone: Lectures: Tuesdays & Thursdays, 3:30 PM - 4:45 PM Office hours: Mondays & Fridays, 3:30 PM – 4:30 PM TA: Jhih-An Yang Class # 2

2 Using iClickers Everyday: swap clicker code to DC Wait for 1 st clicker question to open Hold down On/Off Switch 4 seconds Flashing blue light: hit D C Type in Answer. you’re set for rest of class period DO NOT TURN OFF CLICKER FOR CLASS (o.w. repeat above for any new clicker question)

A Light-ning Blitz through the course material 3 Let’s see some of the major things we’ll cover in the class.

4 Light rays and what we “SEE” Straight-line paths and what enters the eye.

5 Electromagnetic spectrum c = f Wavelength Frequency Speed of light

6 Electromagnetic waves can have any wavelength Scientific notation is useful!

7 Shadows, reflection, refraction – Ch. 2

8 Lenses and mirrors – Ch. 3

9 Precise mathematics let’s you DESIGN lens systems.

10 Photography – Ch. 4 Image recording - digital

11 The Eye – Ch. 5 Visual systems in other creatures.

12 Optical instruments – Ch. 6 Telescopes

13 The “Very Large Array” ‘near’ Socorro, NM.

14 Optical instruments – Ch. 6 Microscopes Robert Hooke’s circa 1660 Modern laser confocal

15 Your eyes can play tricks on you – Ch. 7

16 Visual Processing – Ch. 7

17 Visual Processing – Ch. 7

18 Color – Ch. 9

19 Color perception – Ch. 10

20 Color perception – Ch. 10 The sum of the two number is: A) 18 B) 20 C) 23 D) 25

21 Scattering & Polarization – Ch. 13

22 Holography and Lasers – Ch. 14 & 15

Break for 7 th inning stretch. Something to ponder during the stretch: WHY (and how) do we see things? 23 Favorite answers: Because… Because there is LIGHT… Because we have EYES… Because creatures that see tend to survive… We want to understand these things

First goals of the course: Understand enough about light to be able to talk about it. Develop our first model for how light behaves and how we SEE things. 24

Disappearing glass rods…

Cloaks of invisibility? 26

What do you already know about light? Spectrum Wave and particle properties Source of energy momentum Fast speed Straight line unless it interacts 27 Please, make a list with :

Laser Flashlight Light bulb Incident ray from a light bulb MANY reflected rays come from all parts of Alex, including his nose - a diffuse object Bob sees Alex's nose because a reflected light ray enters Bob's eye! Light rays are invisible unless they enter directly into our eye or are scattered by smoke, fog or some object into your eye!

Rays bounce when they reflect off a mirror or shiny surface Mirror This is called specular reflection. How is it different from diffuse reflection?

30 To understand light better we need to know about Waves Electric fields Magnetic fields Light is an ‘electromagnetic wave’ E B

QUALITATIVE things about electric forces 31 A)There are two types of charge B)There is only one type of charge C)There are more than two types D)None of the above. A)Like charges attract B)Like charges repel C)Opposite types repel D)Depends on the situation. And opposites attract

QUANTITATIVE statement: 32 Coulomb’s Force Law: q Q r Constant of nature. Depends on the charges distance What is the force that q feels from Q ?

A question: 33 You are given three numbers, a, b, and c. True or false: The combination of numbers A) TRUE B) FALSE is always equal to: Experiment: Try some actual numbers, like a=2, b=3, c=4 and test it.

34 You are given four numbers, a, b, c, and d. Which of these are valid ways to rewrite A) B) C) D) E) All of the above None of the above Experiment can be valuable here too…

QUANTITATIVE statement: 35 Coulomb’s Force Law: q Q r Constant of nature. Depends on the charges distance What is the force that q feels from Q ?

Useful to rewrite things: 36 Coulomb’s Force Law: Which is another way to write this force law? A) B) C) D) E) None of these All of these

The universe divides into two parts: 37 Coulomb’s Force Law: Property of the local THING, say YOU. Properties of the rest of the universe. We Say: ELECTRIC FIELD due to the rest of the universe.

Suppose we have 3 charges: 38 The force felt by q … q Q1 r1 A)Can still be F=qE B)Cannot be F=qE C)MAY be F=qE if the charges are in a line. D)Something else happens. Q2 r2

Electric Fields 39 The charge value. Properties of the rest of the universe. We Say that charges feel a force: ELECTRIC FIELD due to the rest of the universe.

What do you already know about magnetism? 40 A)Magnets come with only a north pole B)Magnets come with only a south pole C)Magnets come with both a north and south pole. D)Depends upon the type of magnet. A)Like poles attract B)Like poles repel C)Opposite poles repel D)Depends on the situation. GUESS WHAT: The universe produces Magnetic Fields too.