Download Light Magic – Optics and Vision - New England Board of Higher

OPTICS and VISION
Judy Donnelly
Three Rivers Community College
Nicholas Massa
Springfield Technical Community College
Fenna Hanes
New England Board of Higher Education
ASEE K12 2007
OPTICS and VISION
TODAY’S AGENDA
Introductions
A little bit about light
Color activities
BREAK
What do optical engineers do?
Optics activities
ASEE K12 2007
OPTICS and VISION
A WORD FROM OUR SPONSOR…
New England Board of Higher EducationProjects PHOTON, PHOTON2 and PHOTON PBL
These activities are favorites of the teacher
participants of the PHOTON projects:
Middle school
High School
College- distance learning
Teacher Professional Development
ASEE K12 2007
What can you do with light?….
ASEE K12 2007
SO WHAT IS LIGHT?
Nobody really knows!
So, we just describe its behavior:
 Sometimes it acts like a wave
 Sometimes it acts like a particle
 Sometimes we can ignore both waves
and particles and say it’s a “ray” that
obeys geometric laws
ASEE K12 2007
When we talk about light colors, we
refer to the wavelength of the light.
Wavelength is the distance from one peak to the next.
Ocean waves have wavelengths around a meter or two.
Bathtub ripples have wavelengths around a centimeter or two.
What about light waves?
ASEE K12 2007
Wavelengths of visible light waves are less than one
micrometer (0.000001 m)!
This is one micrometer!
This is a hair. (about
80 micrometers in diameter)
This is the wavelength of
blue light (0.5 micrometer)
ASEE K12 2007
Visible light is part of the
Electromagnetic Spectrum
The regions of the spectrum overlap somewhat.
The visible portion is a very small part of the total
spectrum!
ASEE K12 2007
The Colors of the Visible Spectrum
Red
Orange
Yellow
Green
Blue
Violet
Remember “Roy G. BV”
ASEE K12 2007
Colors we can’t see are important
to science and technology.
Black-Eyed Susans in visible and ultraviolet light
Cleopatra butterfly in visible and ultraviolet light
From Alien Vision by Austin Richards
SPIE Press, 2001
ASEE K12 2007
Colors we can’t see are important
to science and technology.
Infrared image from Boston University Center for Subsurface
Sensing and Imaging Systems. The image is color-coded for easier
interpretation. Why are the eyeglasses black?
ASEE K12 2007
Light and matter
When light encounters matter, it may be:
Reflected
Transmitted
All of these may
take place to
some extent
Absorbed
Scattered
ASEE K12 2007
Today’s
1.
2.
3.
4.
experiments*:
What Color is a…?- Seeing colors
Spectroscopy- Colors of light sources
Jello® Optics- Transmission and absorption
The Mirror Game- The geometry of reflection
These topics are addressed in the fifth grade science standards in Connecticut.
ASEE K12 2007
#1: The Colors of “Things”
THE CHALLENGE
•What color is a tomato?
•Why?
•Can you change the color of a tomato? (no paint
allowed!)
THE MATERIALS
•Color LEDs (or flashlight with color filters)
•Pieces of colored candy or paper, fruit, etc
HINT
Darken room if possible. Object can be placed inside a
deep carton if room lights can’t be turned off
ASEE K12 2007
#1: The Colors of “Things”
THE EXPLANATION
The color you see depends on:
•The wavelengths reflected by the object
•The wavelengths present in the illumination
•The color sensitivity of your eyes
White Light
Looks orange
Blue Light
Looks black
ASEE K12 2007
Very Dim White Light
No color vision!
#1: The Colors of “Things”
APPLICATION: Color science is important to display
technology, paint matching, and retail illumination.
Southern Cal Edison Lighting Showroom
ASEE K12 2007
#2: The Colors of Light
THE CHALLENGE
•What colors are given off by a source of light?
•Can you tell what colors are in a source of light just by
looking at it?
Yellow?
ASEE K12 2007
#2: The Colors of Light
THE MATERIALS: Building the “spectroscope”
1. To separate the light into its basic colors, you could
use a prism (difficult!) or a diffraction grating
2. Recycling: use a CD with the label stripped off! (This is
a type of diffraction grating.)
3. To block out other nearby light sources, use a short
cardboard tube.
4. To separate the colors so they don’t overlap, use a slit.
Light source
slit
tube
ASEE K12 2007
CD “grating”
look in here
#2: The Colors of Light
SAFETY HINT:
•Don’t look at the sun or into a laser!
THE EXPLANATION
Different types of light use fundamentally different
processes to create light. The colors seen depend on the
type of source and the source materials (type of gas,
semiconductor, etc.)
• Heat (incandescent bulb)
• Glowing gases (neon lights, sodium street lamps)
• Fluorescent bulbs- the color is determined by the
phosphor coating on the inside of the bulb
• Light emitting diodes (LEDs)
• Lasers
ASEE K12 2007
#2: The Colors of Light
APPLICATION
Substances can be identified by the colors they give off
when they are heated, or by the colors they absorb.
194 nm
284 nm
304 nm
UV images of the sun from the SOHO web site
http://sohowww.nascom.nasa.gov/
http://honolulu.hawaii.edu/distance/sci122/
ASEE K12 2007
ASEE K12 2007
#3: Jello® Optics
THE CHALLENGE
•How does a lens work?
•How does an optical fiber work?
THE MATERIALS
•Jello® Jigglers (can be made with plain gelatin)
•Stiff plastic or cookie cutters
•Laser pointer or small focusable flashlight
HINT
Keep cut edges flat and smooth for best results.
Clear plastic pieces are available from science supply
companies if gelatin is too messy.
ASEE K12 2007
#3: Jello® Optics
SAFETY HINT:
•Don’t look into the laser or shine it into anyone’ eyes!
THE EXPLANATION
•Light slows when it goes from air into the gelatin
•The slowing leads to a bending of waves
•Consider a marching band, going from pavement to mud…
Mud
"normal
line"
Paved
ASEE K12 2007
#3: Jello® Optics
THE EXPLANATION (With Math)
• Snell’s Law:
n1sinθ1 = n2sinθ2
• From air to gelatin: Bends toward the normal
• From gelatin to air: Bends away from the normal
θrefr
θrefr
θincc
θinc
n1
fast
n2
slow
n2
slow
ASEE K12 2007
n1
fast
#3: Jello® Optics
APPLICATIONS
• Lenses
• Optical Fiber (Total Internal Reflection)
ASEE K12 2007
#4: Hit the Target
THE CHALLENGE
•How does a mirror work?
•How can you use a mirror to steer a light beam?
THE MATERIALS
•Plastic mirrors mounted on blocks
•Laser pointer
•Target
•String, protractor, meter stick, tape
HINT
You don’t need to use all of the materials. Use what
you think is most helpful.
ASEE K12 2007
#4: Hit the Target
SAFETY HINT:
•Always know the location of the laser beam. Let
everyone know when you are turning the laser on.
THE EXPLANATION
• Law of reflection: θincidence = θreflection
θincidence
θreflection
ASEE K12 2007
#4: Hit the Target
APPLICATION
“Optical Levers” used to steer light beams
ASEE K12 2007
Resources for teaching optics
Web sites with information and activities
www.nebhe.org
www.opticsforkids.org
www.opticsforteens.org
www.hands-on-optics.org
www.lasertechonline.org (links at bottom right)
Free posters and career materials
Available at www.spie.org and www.osa.org
List of optics tutorials and Java/Flash applets
http://www.lasertechonline.org/optics_links.html
College and career information
www.qcc.cuny.edu/physics/lfot/LFOT_FAQs.asp
www.opticseducation.org/
ASEE K12 2007