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Office: Gamow Tower, F-521 Email: email@example.com Phone: 303-492-7277 Lectures: Tuesdays & Thursdays, 3:30 PM - 4:45 PM Office hours: Mondays & Wednesdays, 3 PM - 4 PM Grading Assistants: Jian Yao, Yiheng Lin, Hao Song.
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Why is learning science like learning a foreign language?
Words have new and precise meanings
Wave, image, ray, lens, white, exposure, file, see, reflection, refraction, dispersion, particle
What does it mean for the "sun to set?" Is there really global warming? How could complex and magnificent creatures like us have evolved from lower species?
We all have scientific curiosity:
Why the sky is blue?
What is rainbow?
What is sunset?
How my laptop display works?Physics 1230: LightandColorIvan I. Smalyukh
Ornithoptera goliath supremus, f. titan
Papilio blumei blumei
Ornithoptera priamus urvillianus
HW#1 due next Thursday
I have had no physics in high school or college
I have had physics in high school but not in college
I have taken a physics course OR a psychology course at the college level
I have taken more than one physics or psychology courses (high school and/or college level)
I am a science majorSurvey to be answered by clickers
Because of requirements by the university
Because it was recommended to me
Because it looked easy
Because it looked interesting
I don't know whySurvey to be answered by clickers
103 = 1000
102 = 100
101 = 10
100 = 1
Or very small numbers
10-1 = 0.1
10-2 = 0.01
10-3 = 0.001
Scientists don't use feet or miles to indicate distances
1 meter = 39.4 inches
1 km = 1000 m = 0.625 mi
1 cm = 10-2 m = 0.394 inches
1 mm = 10-3 m
1 nm = 10-9 mScientific notation and metric system
500 nm = 5 x 102 x10-9 m = 5 x 10-7 m
1 cm = 10-2 m;
Hence, 10-2 /(5 x 10-7) = 20,000 wavelengths in a cmClicker question
Other waves: rope waves, water waves, sound waves, etc.
Sometimes EM waves are called EM radiation
Radar and similar waves
cell phone waves
Infrared or heat waves
Ultra-violet (suntan) waves
EM waves are created and destroyed by emission and absorption
Classical picture (Phys 2000)
wiggling electrons radiate radio waves or radar waves
electrons in an atom are resonant with emitted or absorbed light waves or X-rays
Quantum picture (Phys 2000)
change of state of electrons in atoms when bundles of wave energy (photons) are emitted or absorbed
Incandescent light bulb
Fluorescent lightIntro and Chapter 1 Continued
Ray from a laser acts like a single light ray
Illustrate by laser light through fog
Bounce off mirror
Bounce off white card
Put through water (bending)
We only see light when a ray enters into our eye
Laser light is visible from side because it is scattered into our eyes
Rays from a flashlight
Rays from a light bulb
What about light coming from everything in this room? Two kinds of objects:
Self luminous objects (lights)
Objects which are not self-luminous are seen because of light reflected off them
Turn out the light and we don't see anything in the room
It's all reflected light with many rays coming from diffuse surfacesRays(a single beam of light, for example)
Seeing everything in terms of rays
MANY reflected rays comefrom all parts of Alex, includinghis nose - a diffuse object
Incident ray from a light bulb
Bob sees Alex's nose because a reflected light ray enters Bob's eye!
Created by oscillation of my hand holding the rope
Finite speed of wave, but rope segments do NOT move in direction of wave
Rope segments move up and down, not along wave
Note the change that occurs when I oscillate my hand faster
Radio wave transmitter
3 meters wavelength
(100 Mhz frequency)
Google search under keyword "physics"
Water waves (circular pattern)
• The period, T, is the time for the wave to make one complete cycle (say, top-bottom-top) AT ONE FIXED SPOT
• The frequency, f, of the wave is equal to one over the period: f = 1/T
f has the units of 1/secs, which we call Hertz (Hz)
• The frequency, f, is related to the speed of the wave, c and its wavelength, (lambda):
Think of my hand moving to make the rope wave. The period is the time for my hand holding the rope to make one complete top-bottom-top (or bottom-top-bottom) motion.
f = c
Light with wavelength of 650 nmappears red when it enters a viewers eye
Light with wavelength of 520 nmappears green when it enters a viewers eye
Light with wavelength of 470 nmappears blue when it enters a viewers eye
The speed of light in empty space is the same for all wavelengths
Which of the light waves is brightest?
Which of the light waves has the highest speed in empty space?
They all have the same speedClicker questions
Light with both wavelengths 650 nm and520 nm appears yellow when it enters a viewers eye
Light with only wavelength 580 nm
ALSO appears yellow when it enters a viewers eye (A DEEPER YELLOWTHAN FOR THE CASE ABOVE)
Light which is a mixture of 650, 520 and 470 nm wavelengths (and possibly more wavelengths) appears WHITE when it reaches your eye
No single wavelength (mono-
chromatic) waveappears white
when it reaches your eye!
Wavelength = 10 million nm
= 3 x 1010 Hz
Filament with current of electrons which hitinto atoms causing light to be emitted
Light emitted at many different resonance frequencies of atoms appears as white light
Electrode leading to the other side ofthe wall plug
Electrode leading to oneside of the wall plug
Wherever it intersects a ray the wavefront is perpendicular to that ray
More technically, the tangent to the wavefront at the point of intersection is perpendicular to the ray
The wavefront may be easier to visualize than the rays
You throw a pebble into a pond. The circularly expanding water waves are the wavefronts
When rays come out in various different directions from an object or objects, the wavefront is defined as a curve or surface perpendicular to all the rays
WaveformHow are wave wiggles related to rays?
Light with a SINGLE
wavelength is called
They are perpendicular
Speed of light in empty space is c = 186,000 miles/sec = 3 x 108 meters/sec
Note, the wave is NOT "red." I have colored it red.
We perceive it as red because of its wavelength.