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.