opt light and - weebly

Light and Opt

I- What is Light?

1. Iflvesfjg the nature of light and Vision; and describe the role ofinvention exp1atio

nqUT ifl developing our current Owledge0 / Topic 2: Reflection

2. Investjte the transmissi of light, and describe its behaviour usi ageometric ray model

Topic 3: Refraction

2. Investigate the transmission of light, and describe its behaviour using ageometric ray model

-

Part A: What is light?

Light is a form of energy that allows us to see. Sources oflight (where it comes from) can be natural or artificial.The sun is a natural light source and a light bulb is anartificial light source.The basic properties (characteristics) of light are:• it is a form of energy• it travels in straight lines• it can be reflected

-• it can be bent

Before you start working through this unit, quickly write down all of the thingsyou know about how light behaves. Think about interesting things you haveseen light do or ways that you have played with light.

2. Write two questions about light that you think will be answered in this unit oryou would like to know the answers to.

Did you know?We often think of hurtful things when we hear the wordradiation, but it Is actually a scientific word that describeshow l[ghf moves away from the sun. The sun creates light,and this light radiates outwards from the sun. The light raysspread out in all directions like the spokes In a bike wheel.

Copyright © Resource Development Services, Edmonton Public Schools, 2004. Grade 8 Light and Optical Systems

Brainstorm!

I

in P0 source ofnatural light Where does Iigtitcome from?During daylight, the sun’s rays heatand light up the earth. Shut your eyes tight— au you can see is darkness. Now openyour eyes again. If it is daytime, you will see that light is allaround you.

Natural lightAnything that gives off a light that we can see is called a lightsource. The light sources that are not created by people arecalled natural light sources. They include the sun and thestars. During the day, the rays of the sun light up the earth.Sometimes, if there are no clouds, you can see the starstwinkling in the sky at night.There are other sources of natural light, too. In some parts ofthe world, you can find insects called fireflies. They give off apale, greenish-yellow light that flashes or glows in the dark.Even deep down in the sea, some of the fish are able toproduce flashes of light in the darkness. And if you live in theextreme northern or southern regions of the world, you mightbe able to see the aurora, a dazzling display of colored lightsthat flicker in the sky at night.

Artificial lightThere are also many light sources that don’t occur naturallybut are created by people. These are called artificial sourcesof light. Electric lights, oil lamps, and even candles are allartificial light sources. You can find your way in the dark byusing a flashlight powered by batteries. Television andmovies are made by using light. And city streets are often fullof artificial lights—vehicle headlights, brightly coloredadvertisements, streetlights, and neon lights.Light does more than just enable us to see. We use beams oflight to cut metals into complicated shapes, orto performdelicate surgical operations! Light even helps us to remainhealthy. When sunlight shines on our skin, our body makes avitamin called vitamin D, which helps our teeth and bones togrow healthy.

Artificial sources oflight are createdby people. Light travels throughthreads ofglass1 called opticalfibers. Each fiberis only ½5lflCh(1 mililmeter) thick

Topic 1 - What is Light?• Light plays a central role in our existence

• Light is the form of energy you can see. This energy can beproduced by the sun. stars or fir. or

___________

by light-producing technologies, like batteries.

• Light is often calledby

because it travels

• Radiation is

zcç

Topic I What is Light.notebookFebruary 07, 2013

0• The sun not only lets us see things - but keeps the planetwarm and enables plants to carry out photosynthesis.

• Since photosynthesis plays an important role in the oxygencycle - returning oxygen to the atmosphere 4 ourexistence depends upon the light from the sun1

Basic Photosynthesis.‘ —


0

The First Basic Principle of LightLight is a form of

_________

- When light reaches a surface it canbe

_______________

Electrical energy:

Thermal energy:

-

Chemical energy:

The amount of energy a surface receives depends on theintensity of light.The more the intense the light --- the more light can beabsorbed.

Some Basic Properties of Light

Jght £ourc

--

-fr------

----

----------—-------------—

---

-1

-fr

-fr

-fr

0

Sources of Light1. Naturat Light Sources

.

-4

2. Artificial Light Sources.

________________

heat causing a filament of metal to glow -visible light

Electrical energy 4 Thermal energy 4Visible light energy

______________

Ultraviolet light is absorbed byfabric particles, which in turn emit some of theenergy as light - glowing.

Ultraviolet light energy 4 Energy absorbed by particles 4Visible light energy

,: light energy is stored and released later

____________________:

light energy released by- c&ctionseggtow-s-t-icks-

as visible light paint

0Chemical energy - Visible light energy

/11 U1i)I—


The Ray Model of Light1 basic principle of light:

______________________H

2nd basic principle of light: ‘

Is

• Because of thsprincip e therny mode of light an expanproperties of light.

Ray biagrams• A ray (or ray diagram) shows

____

are straight line(s) that representsThey

• The ray model helps to explain

______________.

If a lighthits an object, it can’t go any further - thus

• They explain why the

_________________________

of lightchanges with distance.

• The type of

_____________

will determine how the lightwill continue.

• Light travels in until it strikes a surface.

Light Interacting with MaterialsIf the surface is

______________,

the light continues in a straightpath through the object

If the surface is

_____________,

the light will be diverted(refracted) after it passes through

Ex. Frosted glass, tissue paper, stained glass

• If the surface is

__________

not allowed through the objthe light will be blocked and

Ex. Glass or Clear Plastic

0

N

Ex. People, rocks

How does light travel?Light travels in straight lines. It always travels like this unlessit meets something that makes it change direction. One way inwhich light can change direction is by reflection. Can youthink of an object that reflects light? We see the things aroundus because of rays of light that are reflected into our eyes. Lightrays travel in straight lines from the object at which we arelooking and into our eyes.

Can light travel around corners?The thin beam ofstrong ilght travelsin a straight line until it hits this hand.This light is reflected off the handandthen travels in a differentdirection.

Imagine what it would be like if light could travel aroundcorners! You would be able to see what is happening upstairsin the bedroom when you are standing downstairs in thekitchen. You could also see around a bend in the road.Crossing the road would be easy!

0Find out more by looking atpages 28—29

3. Switch off all the lights and switchon the flashlight. It will light up only avery small area.

Reflecting light

Light travels in straight linesYou can show how light travels in straight lines, using aflashlight. It is best to do this experiment at night.

S nd behind a doorway and hold up a mirror‘ee what is happening in the next room.

.1 gh t rays reflected from objects in the nextrcnrn are reflected again by the mirror intour eyes.

‘ i sand other diagrams in this book show lighttys as straight lines. The arrows indicate the(1 Unction in which the light travels.

Iapin

a piece of thick, black paper

a flashlight

some adhesive tape

13

2. Fasten the paperover the head ofthe flashlight with adhesive tape.

1. With the pin, make a hole in thecenter of the black paper.

If rays of light didn’t travel instraight lines, the light comingout through the hole wouldspread out and light up much4. Tear off the paper. The flashlightmore of the room. Instead, thewill now light up a much bigger area.light from the pinhole lights uponly a small area.

/\

/1

Topic 2 Reflection.notebookFebruary 07, 2013

0

Topic 2: efIectionfteflection -

Incident ray -

cE5 1ay-

Jan 22.12:22 PM

I


In order to correctly measure the angles of the incident ray and thereflected ray you need to draw a reference line called the normalThe normal is drawn perpendicular (or at a right angle) to theh reflecting surface at the point where the incident ray hits thesurface.

The angle of incidence is measured from the normal to the incidentray.The angle of reflect on is measured from theiior a[to-th ef1ected

**Note- It is important to measure these angles always from thereference line or the normal because you are not always going to havea smooth reflective surface. If you measure from the reflectivesurface to the incident ray or reflected ray the diagram that youhave drawn will not correctly show how materials reflect.

CJan 22-12:35 PM

2

41,

4. 1 ExpIok rning

Name: Date:

Student Exploration: Ray Tracing (Mirrors)

Vocabulary: concave mirror, convex mirror, focal point, magnification, real image, reflect, virtualimage

Prior Knowledge Questions (Do these BEFORE using the Gizmo.)For these questions, it would be helpful to have a metal spoon on hand. If you don’t have one,try to imagine looking at yourself in a spoon.

1. Look at yourself in the front of the spoon (the side where the food sits). What do you see?

The front of a spoon is an example of a concave mirror.

2. What do you see when you look at yourself in the back of a spoon?

The back of a spoon is an example of a convex mirror.

Gizmo Warm-upThe Ray Tracing (Mirrors) Gizmo TM shows a side viewof a light bulb positioned to the left of a mirror. Light rayspassing from the light bulb to the mirror are shown.

To begin, select the Concave mirror. Turn on Colorizelines. Under Show lines, turn off the Central line andthe Line through focal point so that only the Parallelline is showing.

-25 -‘20 -15 -10 -5

1. The blue dot in front of the mirror is the focal point of the mirror. Move the light bulb on theleft around. What is always true about the ray that is reflected from the parallel ray?

2. Turn off the Parallel line and turn on the Line through focal point. Move the light bulbaround. What do you notice about the reflected ray in this situation?

3imOS

Get the Gizmo ready:Activity A: • Check that the Concave mirror is selected.Real and virtual • Turn on the Parallel line Central line and Lineimanes through focal point.

. Place the light bulb above -24 on the central axis,with the focal point at -12. -20 15.,

Introduction: A concave mirror is also called a “converging mirror’ because it reflects light raysinto a point. A real Image is formed where the reflected light rays converge at a point. Unlike avirtual image that forms behind a mirror, a real image can be projected onto a screen.Question: How do mirrors create real and virtual images?

1. Observe: In its current configuration, the distance from the light bulb to the focal point isslightly more than 12 units. The distance from the focal point to the mirror is exactly 12 units.A. What do you notice about the size of the light bulb’s image?

____________________

B. What do you notice about the orientation of the light bulb’s image?

_______________

2. lnvesticiate: Complete each action described in the table below, and state how that actionaffects the image.

Action Effect on imageMove the light bulb to the left.Move the light bulb to the right.Move the focal point to the left.Move the focal point to the right.

3. Analyze: Examine the results recorded in your table.

A. In general, how do the size and position of the image change when the distancebetween the light bulb and the focal point increases?

B. In general, how do the size and position of the image change when the distancebetween the light bulb and the focal point decreases?

(Activity A continued on next page)

0

;izmos

Activity A (continued from previous page)

4. Explore: Move the light bulb to -10 and the focal point to -20. What do you notice about theimage when the light bulb is between the focal point and the mirror?

The image is virtual because no light rays are focused there. This virtual image is what anobserver would see looking into the mirror. The dashed lines represent the direction that anobserver would perceive the reflected light was traveling from.

5. Investipate: Select a Convex mirror, and turn off the Original light lines and the Apparentlight lines. Move the light bulb back and forth (but keep it close to the central axis).A. What do you notice about the three lines reflected from the convex mirror?

B. Is the image of the light bulb a real image or a virtual image? Explain. (Hint: Recallthat a real image is formed where actual light rays are reflected.)

C. Move the light bulb back and forth. No matter where the tight bulb is located on thecentral axis, what is always true about size of the image?

6. Apply: Which type of mirror would you use for the following applications, and why?A.

Cookinga hot dog:

_____________________________________________________

B. Surveillance in a convenience store:

_______________________________________

IXflO%

Part E: How does reflection work?

4ReflectionReflection is a process where light hits a surface and then bounces back off that surface.How the reflection process works depends on how smooth the surface is. Seeing our imagein a mirror and reading the words on this page both involve the process of reflection. Wesee different things because the two surfaces—glass and paper—are very different. Glass isvery smooth and reflects light rays straight back. Paper (when you look at it with amicroscope) is very rough, so the light rays bounce off in all directions. When light bouncesstraight back, you see a “copy” of the image in front of it. When light bounces off indifferent directions, you see what is on the surface (e.g., writing on a page).In the reflection process rays of light are gwen different names depending on the ‘ob” theydo, for examplef

Incident (in-si-dent) RayThe ray of Hght that first hits the surface.Reflected RayThe roy of light that bounces off the surface The straight path (line) that each ray of lighttravels along Is compared to the “normal” ilne and then described as an angle.Normal iJne

V

A straight perpendicular line (90 degrees from the surface) that extends (goes out) fromwhere the incident ray hit the surfaceAngle of Incidence0 The difference between the line that the incident ray followed and the normal line (calledan angle because it’s measured in degrees).Angle of Reflection

V

The difference between the line that the reflected ray followed and the normal line

Study the diagram below and then answer the questions on the next page.

normal

angle of angle ofincidence reflection /incident ray

reflected ray

reflecting surface ICopyright © Resource Development Services, Edmonton Public Schools, 2004. Grade 8 Light and Optical Systems

10

Use the information on the previous page to help you answer the followingquestions. Label questions that are True with a T and questions that are False withonE.

1.

___

The ray of light that bounces off a surface is called the reflected ray.2.

___

The ray of light that bounces off a surface is called the incident ray.3.

____

The ray of light that first hits a surface is called the reflected ray.4.

____

The ray of light that first hits a surface is called the incident ray.5.

____

The normal line is a straight, perpendicular line that extends fromwhere the incident line hits the surface.

6.

___

The angle of incidence is the difference between the path of thereflected ray and the path of the incident ray.7.

___

The angle of incidence is the difference between the path of theincident ray and the normal line.

8.

___

The angle of reflection is the difference between the path of thereflected ray

, 9.

___

The angle of reflection is the difference between the path of thereflected ray and the incident ray.

Consider the following question:

Is the angle of Incidence always the same as the angle of reflection?Using the planner on the following page, design an experiment to find the answer tothe question above. Consider the following things:

• What is your hypothesis (guess)?• What reflective surface will you use (e.g., mirror)?• What other materials will you need (e.g., flashlight, dark room, measuringdevices)?• Do you know how to calculate a 90 degree angle and draw a “normal”line?• Do you know how to measure your angles using a protractor or will youneed help? Will you reflect a beam onto a piece of paper and trace thepath of the light with a pencil?

Cpvright © Resource Development Services, Edmonton Public Schools, 21)1)4. Grade 8 Light and Optical Systems11

28

Aperfectmirrorimage of the

Mirrors and reflectionwater.

Stand in front of a mirror. What do you see? There seems to bea face just like yours behind the mirror. You are looking at areflection of your face.You can see things around you because light is reflected fromthem and then enters your eyes. Mirrors are very good atreflecting light The light that moves from your face towardsthe mirror is reflected back by the mirror and enters your eyes.There seems to be another you behind the mirror because thelight has come back to its source — you

Mirrors are made from a sheet of glass with a shiny metalcoating on the back. It is this layer of metal that reflects thelight. Most mirrors are flat, so the reflection, or image, of anobject looks the same size and shape as the object itself. Thistype of mirror is called a plane mirror.

29

ImagesatanangleWhen you look in a mirror that is set at an angle, you don’talways see yourself. You might see a different image. This isbecause the direction in which the light travels is changed bythe mirror. One instrument that uses mirrors to help you seearound corners is a periscope. A simple periscope consists ofa long tube with a reflecting mirror set at an angle at each end.Periscopes are used in submarines, and by scientists to watchdangerous chemical reactions in laboratories.

Make a periscope

1. Cut a square 2 inches (5 centimeters) square, about ½ inch (1.25centimeters) from one end of each oftwo cardboard strips.

3. Cutaslot3inches(7.5centimeters) long along eachdiagonal line. The slot must be bigenough for a mirror to fit into it.

2. Draw a straight line 3 inches (7.5centimeters) from each end of theother strips of cardboard. Then drawdiagonal lines as shown.

4. On a flat surface, lay out the fourpieces of cardboard as shown. Tapethem together.

5. Tape together the two long sides.Fold the assembled boards to make

You will need:four strips of cardboard,12 in (30 cm) x 3 in (7.5 cm)

6. Carefully apply tape to thecorners of the mirrors so they are notso sharp. Push a mirror througheach pair of slots. Make sure thefronts of the mirrors are facing eachother. Put some tape along each slotto keep the mirrors from sliding.

7. Now you are ready to look aroundcorners and overheads in a crowd!

Find out more by looking atpages 12—13

You can make a simple periscope for yourself.

j/5scissors

a ruler

a pencil

adhesive tape

two small mirrors,about3in(7.5 cm) square

abox.

Topic 2 Refiection.notebookFebruary 07, 2013

The Law of Reflection

The law of reflection allows you to predict how light will travelwhen it hits any reflective surface.

Law of Reflection states -

0Jan 22-12:36 PM

3

Forming an ImagePlane Mirror (Flat Surface)

The image formed in a plane mirror is formed behind themirror and is the same size as the actual object. The imageis the same distance behind the mirror as the object is infront of the mirror. The or entat on of the imqgisaffiè abject

Fp

F1

EEl

DATE NAMECLASS

n REINFORCEMENT I What You See Is WhatYou Get

BIM 3-6

Goal • Reinforce your understanding of the principles of reflection.

What to Do1. Use a ruler to draw the reflected images of the objects below.

plane mirror

2. Were there any differences between the object and its image in the plane mirror? Describeany differences, with respect to(a) size

(b) distance from the mirror

(c) orientation

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!OMI! ATTACKZombies are trying to come into the room! Save us! Save us!

There are 4 zombies trying to get in and are located around the room, some are in unexpected places.A new “laser” weapon has been developed but it is not portable. You must reflect the laser into thezombie’s forehead to obliterate them.

You have limited time to kill them all.

Rules

1. Teamsof2to32. Laser position cannot change during the game.3. Laser position changes for each team.4. Must use at least 1 mirror per kill.5. Time limit is 3:00 minutes

—

7. Interference by other teams will result in losing points or losing their turn.Points

10 points per Zombie kill

a. 1 mirrorb. 2 mirrors x2c. 3 mirrors x3

Time bonus points for time remaining. + 1 point per second.

Volunteers

1 score keeper

1 judge (checks to see if target was hit)

1 time keeper stops the clock when all 4 zombies are hit.

Convex Mirror (Bulges Out)When an object is seen through a convex mirror the imageis

__________

and

_______

away than the object actually iswhen viewing distant objects. This is why the mirror onthe side of your car says, objects in the mirror are closerthan they appear”. When looking into a convex mirror

_____________

it magnifies the object being viewed andthe

imageis

______________

ReflecUon from Concave and Convex MfrromCentej of FocalCurviture PoInt

IConcave Mirrors (curves in)

A concave mirror will give an image that is

___________

andup. Also, the image will be

__________

) if viewed very closely. Concave mirrors areused for make up mirrors.

—

CIprr

2,-

-- a

P’n aa.s.

rflt!Gr( )&-v te renIa:g ii iu’Icfli

DArE: NAMECLASS:

BLM 3-8I SCIENCE INQUIRY 1 Blind Spots in an Automobile

Goal • Demonstrate your understanding of angles of incidence and reflection as theyrelate to the position of mirrors in an automobile.

What to DoThe diagram at the right represents a car, witha rearview mirror and a driver-side plane mirror.(Some cars also have a passenger-side mirror, butyou will consider only the driver-side mirror.)

1. Four light rays have been drawn from thethe position of the driver’s eye, off each endof the rearview and driver-side mirrors.(a) Identify on the diagram, the normal

and the equal angles of incidence andreflection for each line. (Which way is thelight travelling?)

-)-Indieat-threas thaderiby looking in each mirror.

2. The dotted line shows the left edge of thedriver’s field of view while looking forward.(a) Does the driver have a blind spot, where a car or motorcyclist could sit and not bevisible to the driver?

(b) What rule should drivers always obey when turning or changing lanes to the left?

Going Further3. At home, have a parent or another driver sit in the driver’s seat of a car. ‘When you standbehind the car, you should be able to see the driver’s eyes in the mirror. Walk around tothe driver’s side and look for the driver’s eyes in the side mirror. Stand on the left side,behind the driver, and look for any place where you cannot see the driver’s eyes in anymirror. Ask the driver if she/he can see you.

(a) On a separate sheet, write a report of your observations about the car’s blind spot.(b) Draw a sketch to show the size of the car’s blind spot.

side mirror.-.‘

of left eye.

F-

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Rough Surfaces

___________

surfaces do not reflect light uniformly. On a roughsurface

___________

lines go off in many directions, each light raythat strikes the surface will

__________

according to the laws ofreflection. The result appears as though the reflected rays wereThey cannot form an image.

Topic 3: Refractionrefraction:

________________________________________________

• Light becauseitchanges- ---when1+ moves between materials that have differentci

_

_

_

_

• Light travels

___________

in more dense materials

• The bending of light makes the object’sappear to be in a

__________________

from wherethe object really is

You will need:aglass

water

a pencil

1. Fill the glass halfway with water.Put a pencil in the glass and lean itagainst the side.

Why did the pencil lookbent when it was in thewater? Light rays speed upas they reach the edge of theglass and change directionbefore reaching your eyes.This makes the pencil lookbent, and the point of thepencil appears to behalfway up the glass!

What is refraction?When light passes from one substance to another, it may alsochange direction. When light rays pass from air to water orfrom water to air, they bend as they pass through the surface ofthe water. This bending is called refraction.

Can you bend a pencil?Can you bend a pencil without breaking it? You can make apencil look as if it has been bent, by putting it in water.

2. Look at the water from the side.The pencil will look bent.

3. Now take the pencil out of thewater. Nothing has happened to itafterall!

C

The angle of refractionLight rays pass through other substances, as well as air and, ater. They travel at different speeds as they pass throughtse substances. As rays pass out of one substance and intoanother, they are refracted.

The amount that light is refracted depends on two things. TheL;st is the color of the light. Red light bends less than othercolors1and violet light bends more. The second is the angle atwhich the light reaches the surface of the second substance.This is called the angle ofincidence.

The angle at which the light leaves the second substance iscalled the angle ofrefraction. Try your experiment again,I ooking at the pencil from a number of different angles. Youv ill see that the pencil seems to bend more at some viewingin gles than at others.

--4Whiiié-

The photographshowsamirage in

the desert in Tunisia. The heat

makes light rays refract as they pass

from cool airdown tothe hotairnear

3 4the ground. This makesyouthink -.

there is a cloud on the sand, but iVs

not really there. It’s a mirage! Theman in the diagram thinks that he

can see a cloud. But rays from the

cloud above are creating a mirage

on the sand infrontof him.

ight ray

_______________________________________

27

Find out more by looking at

pages 12—1314—15

cool air light ray1bentbyhotair mirage

Z.

__________

________

‘I

oud

How Light Bends

• When light travels from a medium into a

_______

one, such as, from air into

________,

it will bend

__________

the normal

• When light

_______

a denser medium it’s directionof travel will bend

_______fromthnorrna[—-

• How much bending occurs depends on the

_______

___________

involved

• The new direction of the light is called the

• When the angle of

__________

(1) increases, theangle of

____________

(R) also increases, but notnecessarily at the same rate!

air

water

water

air

angle ofrefraction

Part F: How does refraction work?

RefractionRefraction is when light bends because it is moving from one type of material to another(usually transparent). “Bent” light still travels in straight lines. It’s just the direction of the linethat changes (think back to what you learned before about anglesj. Light bends becausethe speed at which it is moving changes when it passes through materials that havedifferent densities (a different number àf particles packed info them). The more dense amaterial is, the slower light passes through it. When the light bends, it makes objects lookas if they are in a different position.Think back to the experiment you conducted earlier In this unit, did the water bend thelight? Did the pencil look as if it were in a different position in the water?

Study the diagram below and then answer the questions.

incident ray

refracted ray

1. Is water more dense than air? How do you know?

2. Are the angle of incidence and the angle of refraction always the same?Explain.

Copyright © Resource Development Services, Edmonton Public Schools, 2004. Grade 8 Light and Optical Systems13

RefractionConsider: f-low does the density of a liquid affect the way light refractsImportant information: The more particles packed into a substance, the denser it is.Hypothesis: (check the one you agree with)

C the greater the density, the more obvious the refractionC the lower the density, the more obvious the refraction

Materials:

• four clear cups or glasses• water, water mixed with salt, cooking oil, translucent shampoo• four pencils

Procedure: (record information in the boxes)1. Fill each cup with one of the liquids.2. Place a pencil in each of the filled cups.3. Record your observations (use pictures and words).

1—,- ——---

---

TSa1FWãter Cooking Oil ‘ Shampoo

I I

Analysis/Conclusion:

1. Answer the original question using evidence/examples from your investigation OR prove whyyour hypothesis was correct.

—

I

.

.2. Go back to question 2 on page 13. Check your answer.

Copyright © Resource Development Services, Edmonton Public Schools, 2004. Grade 8 Light and Optical Systems14

DATE: NAME:CLASS:

BL.M 3-10‘lEEiNQuInVEI Refraction

Goal • Review how light bends when it travels from one material to another.

IntroductionWhen light moves from one medium (such as air) to another (such as water), it bends. This iscalled refraction. The light bends because it changes speed when it moves between materiais thathave different densities.

What to DoAnswer each question in the space provided.

1. The diagrams below illustrate refraction. In (a), for example, the light ray travels throughthe air and enters the glass. In (b), the light ray travels up from the water and enters the air.For each diagram, draw the normal line at the point of contact. Measure and label theangle of incidence and the angle of refraction. Then complete the sentences that followfrom the choices in parentheses.(a) air to glass

--

glass

The angle in the air is

____________

(greater/less) than the angle in the glass.The light entering the glass bends

___________

(tozuard/awayfrerm) the normal line.(b) water to air

ar

water


_____________

(greater/less) than the angle in the water.The light entering the Sends

___________

(tozuard/away from) the normal line.

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DATE: NAME:CLASS:

I SCIENCE INQUIRY i Refraction (continued)

(c air to water

7 water

The angle in the air is (greater/less) than the angle in the water.The light entering the f bends

___________

(toward/awayfrom) the normal line.(d) transparent plastic to air

air


___________

(greater/less) than the angle in the plastic.The light entering the airbends

___________

(oward/awyfr)thenormaIiine.---2. Use the terms below to complete the sentences that follow. If necessary, you may use aterm more than once.

greater than towardless than away from

When light refracts, the angle in the air is always

___________

the angle in the othersubstance. Light entering the other substances bends

____________

the normal line.Light leaving a substance and entering the air bends

___________

the normal line.

TOPIC 3BL.M 3.10

Cvperight r 2U 1, l.;rw fiLl Rtrin tietteti, SthwiLav L the McGr--HiL Conper.Lee ‘fl right rcervei.1 66 lL:iS page may he reprct;ced fear lroet te by the perchairt n: this bitk w:thout the wiItta per .i!ton the ptiblishr

Use what you have learned to correctly organize this information in the chart below.Type of Behaviour:

• Absorption• Reflection• Refraction

What happens to the light that hits the surface?• Is reflected off of the surface• Disappears/changes into another kind of energy like heat• Travels through the surface and out in a new direction

What is the surface usually like to make that happen?• Different, transparent material• Smooth, shiny surface• Rough, dark, opaque surface

:1I

:1

Did you know?Sunsets are red, orange and yellow because those are the longest rays of light. As the sundisappears below thehorizon, it gets further away from us so more of the particles (dust, etc.)in our atmosphere get in the way of the light. The shortest rays of light get bounced away. sothose colours “disappear” before the light gets to us and all we see are the longer rays (red.orange, yellow).

Copyright © Resource Development Services, Edmonton Public Schools, 2004. Grade 8 Light and Optical Systems

Type of What happens to the light when it What Is the surface usually like toBehaviour hits the surface? make that happen?

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