shed a little light on light and geometric optics? · laser water’s surface what do you think? 1...

Light and geometric Optics? Shed a Little Light on

Jeffrey Major – Science Department HeadThames Valley District School Board

[email protected]

UDOS10SB0-17-635528-6

Figure Number

Company

Creative

Pass

C11-F02-UDOS10SB.ai

Nesbitt Graphics

4th Pass (final)

Approved

Not Approved

C11-F02-UDOS10SB.ai

IllustratorJoel and Sharon Harris

laser

water’s surface

WHAT DO YOU

T H I N K ?

1 4

2 5

3 6 A luminous object such as a candle radiates light in all directions.Agree/disagree?

Microwaves travel at the speed of light.Agree/disagree?

This diagram accurately shows how an image appears in a makeup mirror.Agree/disagree?

A full-length mirror is necessary in order for you to see your whole body in refl ection.Agree/disagree?

This diagram accurately shows a laser beam refl ecting off a curved mirror.Agree/disagree?

This diagram accurately shows light refl ecting off the surface of very still water. Agree/disagree?

Many of the ideas you will explore in this chapter are ideas that you have already encountered. You may have encountered these ideas in school, at home, or in the world around you. Not all of the following statements are true. Consider each statement and decide whether you agree or disagree with it.

What Do You Think? 461NEL

Using Light Rays to Locate an Image Light rays and the laws of refl ection help determine how and where an image is formed in a plane mirror. A light source radiates millions of light rays in all directions, but you are only concerned with the rays that actually strike the mirror and are refl ected into your eyes. Th ese rays are refl ected off the mirror, with the angle of incidence being equal to the angle of refl ection.

To learn more about producing multiple images of an object in plane mirrors, try the activity below.

SKILLS MENU: Predicting, Observing, Analyzing

Equipment and Materials: two plane mirrors; two mirror supports; ruler; protractor; a die; paper; pencil

1. Place the two mirrors at right angles to each other at the top of the sheet of paper. Place the die directly in front of the right angle formed by the mirrors (Figure 3). Record how many images you see in the mirrors.

2. Gently move one of the mirrors, changing the angle between the two mirrors, until you see four complete images. Draw lines on the paper at the base of the two mirrors. Measure and record the angle between them.

3. Now gently move one of the mirrors until you see fi ve images. Again, draw lines on the paper at the base of the two mirrors. Measure and record the angle between them.

4. Based on your previous results, predict what angle between the mirrors would produce six images, then seven, eight, nine, and so on.

5. Continue moving the mirrors, counting the total number of images, and measuring the angle between the mirrors as long as you are able to.

A. How many images were visible when the mirrors were at right angles to each other? T/I

B. Use your knowledge of light rays to explain why this number of images was formed. K/U T/I

C. What was the angle between the mirrors for four images? T/I

D. What was the angle between the mirrors for fi ve images? T/I

E. Were your angle predictions correct for six, seven, eight, and nine images? If not, explain why. T/I

F. What was the total number of images that you were able to count? Why were you not able to exceed this value? T/I

G. A hall of mirrors in an amusement park seems to produce an infi nite number of images when you look into it. This effect is also commonly seen in elevators that have two plane mirrors on opposite walls (Figure 4). T/I C A

(a) Suggest a reason why elevator designers use this effect.

(b) On a piece of paper, draw two plane mirrors that are parallel to each other. Add light rays to show how this set-up can produce multiple images.

TTRY THIS PRODUCIng IMAgES, AnD MORE IMAgES, AnD MORE IMAgES …

Figure 3

Figure 4 Multiple images produced by parallel plane mirrors

11.7 Images in Plane Mirrors 489NEL

SKILLS HANDBOOK

3.B.

www.PrintablePaper.net

PERFORM AN ACTIVITY

PurposeTo explore the characteristics of images produced by converging and diverging lenses.

Equipment and Materials• converging lens with support• diverging lens• metre stick with two supports• candle with holder• paper screen and holder• second sheet of paper or a small piece of

cardboard• chalk that can be easily erased

ProcedurePart A: Locating Reference Positions for a Converging Lens 1. Place the two metre stick supports under the

ends of the ruler. 2. Place the converging lens in the lens support and

place the lens and lens support in the middle of the ruler (at the 50 cm mark).

3. Aim the metre stick–lens assembly at a relatively distant object that is transmitting external light in the classroom when the lights have been turned off . Suitable objects are the slats of an open window blind, a window frame, or a door frame in a room with a window. Make sure that you are as far away as possible from this distant object. Move the sheet of paper back and forth behind the lens until you see as sharp an image of the distant object as possible. Mark this location on the ruler as F (principal focus). Also, mark in twice this distance (2F) from the lens.

4. Mark these same positions on the opposite side of the lens, but mark them as F ʹ (secondary principal focus) and 2F ʹ respectively.

Part B: Locating Images in a Converging Lens 5. Place a lit candle at these fi ve positions:

beyond 2F ʹ, at 2F ʹ, between 2F ʹ and F ʹ, at F ʹ, and between F ʹ and the lens. Move the paper screen back and forth until you locate an image. Figure 1 shows the setup for this procedure. Describe the characteristics of each image (size, attitude, location, and type) that you were able to locate. Use 2F ʹ and F ʹ as reference points when describing the image location. Record your observations in a table similar to Table 1.

Note that you may need assistance from your teacher for the last two object locations: at F ʹ and inside F ʹ.

When using a candle, tie back long hair and loose clothing.

Place a piece of paper under the candle to catch any falling wax.

Be careful when moving the candle—the wax is hot.

SKILLS HANDBOOK

1.B., 3.B.

Locating Images in LensesLenses are used in many optical devices such as cameras and eyeglasses. In this activity, you will examine the images produced in converging and diverging lenses. Remember to pay particular attention to the four characteristics of images: size, attitude, location, and type (SALT).

13.2

Object location

Size of image

Attitude of image

Location of image

Type of image

beyond 2F ʹ

at 2F ʹ

between 2F ʹ and F ʹ

at F ʹ

inside F ʹ

Table 1 Image Characteristics in Lenses

Questioning Hypothesizing Predicting Planning Controlling Variables

Performing Observing Analyzing Evaluating Communicating

SKILLS MENU

554 Chapter 13 • Lenses and Optical Devices NEL

6. Move the candle back to its original position beyond 2F ʹ. Now cover half of the lens with the second piece of paper or cardboard. Locate and describe the image.

7. Move the second piece of paper or cardboard to cover half of the fl ame. Locate and describe the image.

Part C: Locating Images in a Diverging Lens 8. Replace the converging lens with a diverging

lens. Attempt to fi nd an image on the screen. Now look into the diverging lens, locate the image of the candle, and describe its characteristics. Move the lens back and forth to see if there is any change in image characteristics. Record your observations.

Analyze and Evaluate(a) Where must an object be located for a

converging lens to produce a real image? T/I

(b) What happened to the size of the real image as the object was slowly moved toward the lens from its original position beyond 2F ʹ? T/I

(c) What was the only location where the converging lens did not produce an image? T/I

(d) Where must an object be located for a converging lens to produce a virtual image? T/I

(e) What were the characteristics of the image in the diverging lens for all object locations? T/I

(f) Why did you not have to follow the same procedure for the diverging lens as you did for the converging lens? T/I

(g) Why were you still able to see the object when half of the lens was covered? Why was the brightness of the image reduced? T/I

(h) Why did you lose half of the image when you covered half of the object? T/I

Apply and Extend (i) List some optical devices that use a lens to

produce a real image. A

(j) Name an optical device that uses a lens to produce a larger, virtual image. A

(k) Suppose F for a converging lens is 23 cm, and a luminous source is placed at diff erent positions in front of the lens. Predict the image characteristics for each position. T/I

• 64 cm from the lens• 40 cm from the lens• 10 cm from the lens

paper screen

lens

image

source

Figure 1

13.2 Perform an Activity 555NEL

1

Light and geometric Optics?Shed a Little Light on


[email protected]

Shed a Little Light on the Grade 10 Optics Unit (SNC2D & SNC2P) Time:12:30 PM - 1:30 PM Location: International C

Are you new to optics? Explore how light interacts with mirrors and lenses. Use ray diagrams to predict image characteristics and test your predictions through hands-on inquiry. Computer simulations will be used

to aid conceptual understanding. Support material will be provided.Presenter: Jeff Major

Session Number: 2313

Hands-On: Students are actually allowed to perform science as they construct meaning and acquire understanding.

Light and geometric Optics?How do we engage students in

2

Minds-On: Activities focus on core concepts, allowing students to develop thinking processes and encouraging them to question and seek answers that enhance their knowledge and thereby acquire an understanding of the physical universe in which they live.


Authentic: Students are presented with problem-solving activities that incorporate authentic, real-life questions and issues in a format that encourages collaborative effort, dialogue with informed expert sources, and generalization to broader ideas and application.


•simply "studying the content of science" is not the same as learning science.

•knowledge of facts is important, facts must be learned within the context of authentic experience


3

Light and geometric Optics?Shed a Little Light on


[email protected]

Rationale for Connecting to Outside World

Scientific literacy is achieved when students…use their knowledge and skills to purposefully plan and take action in the communities aimed at enhancing personal wellbeing and promoting the betterment of society and the environment.

Science Education: A Summary of Research, Theories, and Practice

4

The science curriculum has a crucial role to play in teaching them [students] how to exercise the enormous power of technology responsibly, carefully and compassionately, and in the interest of all living creatures.

– D. Hodson

Rationale for Connecting to Outside World

5

Predict, Explain, Observe, Explain

YES NOJeff

SteveJen Mark

MikeAmy

Sue

6

http://www.uvm.edu/~mfuris/INTRO_PHYSLETS/contents/optics/applications/illustration36_1.html

http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=373

Producing images with two plane

mirrors.

7

How Large Does A Mirror Need To Be To Show Your Entire Body?

8

The following diagram illustrates that the minimum length of a plane mirror required for someone to view

their entire image equals half their height. Note that the top of the mirror should be placed at eye level.

http://www.batesville.k12.in.us/Physics/PhyNet/Optics/Reflection/Mirror_Size.html

9

http://www.nelson.com/onsciencepd/

10

http://pages.physics.cornell.edu/courses/p101-102/p102/14/java/concave/index.html

http://pages.physics.cornell.edu/courses/p101-102/p102/14/java/convex/index.html

http://www.phys.ufl.edu/~phy3054/light/lens/applets/convlens/Welcome.html

http://www.phys.ufl.edu/~phy3054/light/mirror/applets/cavemir/Welcome.html

http://www.phys.ufl.edu/~phy3054/light/mirror/applets/convmir/Welcome.html

http://www.phys.ufl.edu/~phy3054/light/lens/applets/divlens/Welcome.html

11

http://webphysics.davidson.edu/Applets/optics4/default.html

The Optics Bench from

Physletsdoes it all:

plane mirrors, curved mirrors,

and lenses.

Where is the

filament in a car

headlight really

located?

The Optics Bench at Physlets lets us answer this:http://webphysics.davidson.edu/Applets/optics4/default.html

12

http://www.physics.uoguelph.ca/applets/Intro_physics/kisalev/

Other good optics simulations:

http://www.explorelearning.com/

Gizmos also has optics

simulations.

http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=39.0

Additive and

subtractive colourtheory.

13

http://javaboutique.internet.com/ColorFinder/

Additive colourtheory:

producing any colour

shed a little light on light and geometric optics? · laser water’s surface what do you think? 1...

Documents