Transcript
M R C A M P B E L L
G R A D E 8
OPTICS AND LIGHT
WHAT IS THIS? CAN YOU EXPLAIN IT?
I CAN…
• Identify and describe, through experimentation,
sources and properties of visible light including:
• rectilinear propagation
• reflection
• refraction.
OP 8.1
WHAT DO YOU KNOW ABOUT LIGHT?
• THINK-PAIR-SHARE
• MAKE A LIST OF THINGS YOU KNOW• Sundog explanation
LIGHT
Light can be:
• Natural – bioluminescence, stars, sun, moon
• Electric – incandescent light bulbs, flashlights and electroluminescence (LED)
• Chemical – chemoluminescence (glow sticks), fluorescence (fluorescent light bulbs) and phosphorescence (glow in the dark materials)
• Combustion-based – candles, fire, torches
• Nuclear
FACTS ABOUT LIGHT
• Light Travels in Straight lines and illuminance
decreases with distance from the source.
• Light can not bend around objects pg 93
LIGHT VOCABULARY
• Luminous- objects that produce light. Ex- sun, light
bulb, fire
• Non-luminous- objects that do not produce light
but may reflect it. Ex- moon, most objects on earth
• Transparent- material that allows light to pass
through it. Ex glass, air, filters
• Opaque- materials that do not allow light to pass
through. Ex- wood, metal, thick plastic
• Translucent- material that allows some light to pass
through. Ex- some cloth, stained glass
QUIZ
Label each cup- Opaque, Transparent,
Translucent
SHADOWS
• A shadow is created whenever a light hits an
opaque material
• Shadows have two regions. A partially shaded and
a fully shaded area.
• Umbra- Fully shaded area
• Penumbra- partially shaded- some light is blocked
some light passes by the object
VIDEO
• ROVER- Grade 8 science video “Beings of Light”
DOES DISTANCE MATTER?
• The amount of light arriving at one place per unit
area is referred to as illuminance.
• Lumaninance intensity- (AKA- brightness) refers to
light emitted from the surface of an object Ex-
candle.
• The farther from the object you are the dimmer it
will appear.
PROBLEM SOLVER
• Do problem solver on pg 96 and questions on pg
97-98
CHECK YOUR PROGRESS
• Pg 98 Questions 1-6
I CAN…
• Explore properties and applications of optics-
related technologies, including concave and
convex mirrors and lenses OP 8.2
THE REFLECTION OF LIGHT
• The law of reflection- DRAW THIS
LAW OF REFLECTIONS
• Normal- line perpendicular to the mirror (90degrees)
• Incident Ray- in coming ray
• Angle of Incidence- angle between incoming ray
and normal
• Reflected Ray- ray after reflection
• Angle of Reflection- angle between the outgoing
(reflected) ray and normal
• Investigate these definitions during the lab on page
102-103
REFLECTIONS
• Specular (regular) Reflection- reflection off of
smooth surfaces
• Diffuse Reflection- reflection off of rough surfaces
that cause the reflected light to scatter
CHARACTERISTICS OF IMAGES IN PLANE MIRRORS
• Image size is equal to object size
• Image distance is equal to object distance
• The image is upright
• The image is virtual
REFLECTION AND REFRACTION
• Reflection and Refraction Experiment
• Do questions on page 105
• Interactive Reflection Site
• visual definitions
• Physics definitions of reflection, refraction and light
This is a good site for students to review and study
from. Good reference for facts and understanding.
EXPLORING PLANE MIRRORS
• Supplies- Styrofoam cups, mirrors, tape, popsicle sticks, laser pointer, any other reflective surface
• Goal- make a beam of light reflect off of at least 3 objects and return beside laser pointer.
• Change the distance and angles of your mirrors.
• How many mirrors, can the light reflect off of before it disappears?
• What challenges do you face? What does this activity teach you?
• Try this with several different set ups, combine with others
CHARACTERISTICS OF IMAGES USING CONCAVE MIRROR
These are characteristics of images using concave
mirrors (depends on the position of the object):
• It can be smaller, larger or the same size
• It can be upright or inverted
• It can be real or virtual
CONCAVE MIRROR
Real images are created on the same
side of the mirror as the object
When object is far away, image is upside down.
Pg 108
CONVEX MIRROR CHARACTERISTICS
• Curved outwardly
• Single mirror reflects large area
• Images appear smaller than true size. Example- Bus
Mirrors, surveillance mirror
CONVEX MIRROR
LENSES
• A lens is piece of transparent material that can
bend, or refract, light rays to help form a well-
focussed image.
• Lenses come in different sizes and shapes and are
made of different types of materials. Examples:
camera lenses are made of glass, contact lenses
are made of plastic
• Convex- outwardly curved
• Concave- inwardly curved
CONCAVE LENSES
• Have a surface that curves inward like the inside of
a bowl.
CONCAVE LENSES
Concave lenses are thin in the middle and
make light rays diverge (spread out).
If the rays of light are traced back (dotted sight
lines), they all intersect at the focal point (F)
behind the lens.
principal axis
•F
CONVEX LENSES
principal axis
Light rays that come in parallel to the principal axis converge at the focal point.
Convex and Concave Definition
•F
CURVATURE OF LENSES
The amount of curvature on a convex
lens determines how much the lens bends
the light passing through it. This also
determines the focal length of the lens.
Interactive Example
CONVEX LENSES
Convex lenses are thicker in the middle and focus light rays to a focal point in
front of the lens.
•The focal length of the lens is the distance between the center of the lens
and the focal point.
•For a convex lens, the refracted light rays are often refracted to a common
point. Hence this type of lens is sometimes referred to as a converging lens
(bringing together).
LENSES
The first telescope, designed and built by Galileo, used lenses to focus light from faraway objects, into Galileo’s eye. His telescope consisted
of a concave lens and a convex lens.
Light rays are always refracted (bent) towards the thickest part of the
lens.
convex lens
concave lens
light from object
CONVEX LENSES
Convex lenses are thicker in the middle and focus light rays
to a focal point in front of the lens.
•The focal length of the lens is the distance between the center of the
lens and the focal point.
•For a convex lens, the refracted light rays are often refracted to a
common point. Hence this type of lens is sometimes referred to as a converging lens (bringing together).
IMAGE CHARACTERISTICS CONVEX LENS
(OBJECT BETWEEN LENS AND FOCAL POINT)
S larger than object
P farther from lens than object
O upright
T virtual
Virtual Tour of a lens
CHECK UNDERSTANDING
• Due questions on pg110
I CAN…
• Compare the nature and properties of human vision
with optical devices and vision in other living
organisms. OP 8.3
REFRACTION
• Refraction- occurs when light passes through one
substance into another (ex light passes from water
to air)
PROBLEM SOLVER
• Do activity on pg 113
• Fill a clear cup with oil, another with water
• Place a gummy bear at the bottom
• Use a toothpic to see how easy it is to spear the
gummy bear
1. What differences do you notice?
2. What happens when the toothpick enters the
water? Oil?
WATER REFRACTION LAB
• Lab on page 114
• Follow the steps and Answer all questions
GLASS REFRACTION LAB
Page 116- follow instructions and answer
all questions
REFRACTION INDEX
• Light travels at different speeds through glass and
water
• Refraction index is a measure of how much speed
the light is reduced in the region
MAKING USE OF REFRACTION
• Answer questions on page 118
• Draw a picture of you using refraction in real life
EYE BALL DIAGRAM
• Eye Ball Diagram
• Hand this out and go over the anatomy of an eye
HOW CAN CONCAVE LENSES CORRECT NEAR-SIGHTEDNESS:
HOW CAN CONVEX LENSES CORRECT FAR-SIGHTEDNESS
TYPES OF LENSES
• Convex- Curved outward
• Concave- Curved inward
• Single and double concave and convex lenses
LENS REFRACTION LAB
• Page 121-122
• Do questions on 122-123
INVENTOR OF THE TELESCOPE
Go to Page 132
CAPTURING IMAGES
Read 124-135
LIGHT IN THE EYE
• Light enters the eye through the cornea and is
further refracted through the lens. Here it is flipped
upside down and projected into the retina. The
image remains inverted until it reaches the part of
the brain called the visual cortex. The image is then
processed, enhanced and re configured to the
final image that we see.
• Poke the bottom right side of your eye through your
eyelid. You should see a black dot on the top left
part of your vision.
HOW THE EYE CAPTURES AN IMAGE
CAPTURING IMAGES
VISIBLE LIGHT SPECTRUM
• Prism- transparent and made of glass. Two parallel
triangles and other faces are parallelograms
• ROYGBIV- These are the colours of the visible light
spectrum
SEEING COLOUR
• Read 143—147
• Discuss primary colours, Secondary colours
• Cones- specialized cells in the retina of your eye
• 3 types of cones each are sensitive to different
colour ranges of red, green and blue. When light
hits the cones, the cones send a message to they
brain. The colour you see depends on the type and
number of cones responding to the light entering
your eye.
COLOUR WHEEL EXPERIMENT
This experiment should demonstrate that all colours
together create white light
Colour Wheel Experiment
I CAN…
• Evaluate the impact of electromagnetic radiation-
based technologies on self and community OP8.4
PROPERTIES OF LIGHT
• Consists of colours that can be split and brought
back together
• Moves outward in every direction of light source
• Form of energy
• Eyes can detect it
• Moves in straight lines
• Can be reflected or refracted
• Illuminance decreases with distance from source
PROPERTIES OF A WAVE
• Wavelength- distance between the top of one
wave and the top of the next
• Each colour is a slightly different wavelength
• Do questions on 153
RADIATION
• Pg 154-155
LIGHT SOURCES
• Bioluminescence- natural occurring chemical
reaction takes place within a living thing and results
in the emission of light. Ex- fireflies, glowworms,
starfish
ARTIFICIAL SOURCES
• Chemiluminescent- chemical reation that
produces light
• Ex glowstick
PHOSPHORESCENCE
• Materials that absorb light energy and store it for a
long period of time and then release it in light form.
• Pg 163 for definitions
ELECTROLUMINESCENCE
• When electric current passes through a material
such as a semiconductor and light is emitted.
• Examples- Light Emitting Diodes (LEDs) and Organic
Light Emitting Diodes (OLEDs) Like a wrist watch
back lightOLED
LED
COMMON LIGHT DEVICES
• Incandescent light bulb- uses electrical heat energy
to heat a thin wire called a filament. Because the
filament is too think to carry the electricity easily, it
over heats and glows white hot.
COMPACT FLORESCENT LAMPS
• Contains an opaque tube that is coated on the
inside with a florescent material. The tube is filled
with argon gas and a small amount of mercury
vapor. When you turn on the electricity, UV light is
produced in the tube. When the UV light hits the
florescent material the UV waves are absorbed and
the material then releases the absorbed energy as
viable light.
CHECK YOUR PROGRESS
• Questions on pg 167
• Study for Test using study guide and notes.