Download pdf - Physical Science 2014-2015: Concave, and Convex Mirrorsgalileo.phys.virginia.edu/outreach/ProfessionalDevelopment/UVa... · Joyce Lowry and Vicki Lewis Physical Science 2014-2015:

Joyce Lowry and Vicki Lewis

Physical Science 2014-2015: Concave, and Convex Mirrors Grade Level: 8

Duration: 100 minutes, or two 50 minute classes

SOL(s): 9c The student will investigate and understand the characteristics of transverse waves. Key concepts include images formed by lenses and mirrors;

Essential Knowledge: Plane, concave, and convex mirrors all reflect light. Convex mirrors diverge light and produce a smaller, upright mage.

Concave mirrors converge light and produce an upright, magnified image if close and an inverted smaller image if far away.

Instructional Objectives: SW will identify and compare images formed by concave and convex mirrors. SW draw diagrams of real and virtual images formed by each type of mirror. SW compare and contrast light behavior on plane, concave and convex mirrors.

.

Lesson

Segment &

Time Est.

Materials

Instructional Sequence

Teacher/Student

Actions Introduction

(Predict,

Explain)

Power point with

Images from plane,

concave, and

convex mirrors.

Worksheet with

prediction

scenarios

Predict: Elicit Students’ Prior Knowledge / Ideas:

How are reflections formed? (Image 1 - Show on the screen an image of Escher”s Hand with the

Reflecting Sphere)

What do you see in this picture? How is an image formed? Does the image in the sphere look

exactly like real life? How is it different and how is it the same? How do you think the image in the

globe is formed?

Show on a screen images formed from plane mirrors and ask students to explain how a reflection is

formed? Compare an image formed by a mirror and how we see objects in the room.

Show on the screen images formed by convex and concave mirrors. Ask how these images are

different from the images formed in the plane mirrors and how some of them might be similar to

those formed by convex or concave mirrors.

Display Mirror Mirage of Pig

Pass out handout with predictions and question and allow student time to respond. Tell them they

will have a chance after the lab activities to review their ideas, an or change them according the

what they have learned and our discussions.

T. show ppt Image 1 and

elicits s. prior knowledge of

The Law of Reflection,

Diffuse and Regular

Reflection in a plane mirror.

T. lead discussion to elicit

terminology - concave,

convex, image, reflection, light

rays, focal point

Like the Escher image the

mirage pig should provide

interest and motivation. T. also

lead discussion determine

vocabulary - Real vs Virtual


Explain: Discuss student predictions and answers in class discussion. While validating all

responses, discuss those that seem most reasonable based on what students have been learning.

S. make predictions and

explanations for their

predictions.

T. leads discussion of s.

predictions/explanations.

Body

(Observe)

(Explain)

Lab 1

Spoons

Pencil

Worksheet

Lab 2

Optics Bench

Light Source

Convex and

concave mirror

Paper screen

Worksheet

Lab 3

Computers or iPads

Image simulator

located at:

http://tutor-homework.com/Physics_Help/lens_ray_simulation.html Worksheet

Observe:

1. Pass out lab activity questions/observation worksheet for each of the four labs.

2. Review safety rules (and if using glass mirrors, must wear goggles)

3. Review the directions for each of the activities and demonstrate how to use the simulator.

1. Lab 1 – S will describe the characteristics of images formed by both both convex

and concave mirrors in terms of the images’ size, clarity, upright/upside down

orientation, left/right orientation, and location (real and virtual).

Q. Describe the appearance of your image in the mirror.

Q. How does the appearance of a pencil point change as it moves closer to the

bowl of a spoon?

Q. If a flat mirror reverses right and left, why doesn’t it reverse up and down

2. Lab 2 – S. will collect data and create a graph related to the placement

of object and the formation of the image. S. will compare and contrast

characteristics of images formed by convex and concave mirrors on a Venn

Diagram.

3. Lab 3 – S. will take the settings from lab 3 and input them into the image

simulator and use these to draw ray diagrams of formation of images.

S work in small groups

making observation about

characteristics of images

formed by concave and convex

mirrors.

T. circulates and asks S. about

their observations and

explanations for their

observations and offers help

with adjusting equipment and

using simulations.

http://tutor-homework.com/Physics_Help/lens_ray_simulation.html





Joyce Lowry and Vicki Lewis Closure

(Explain,

con’t)

Total Time =

Explain (continued): Whole-class discussion of small group observations/explanations. Provide

the scientific explanation to students. S. groups will share the results of the three labs with the

whole class. The students will go back to the original prediction sheets, and revised their answers

based on experiences with the labs.

1. Images formed by convex mirrors diverge light and produce a smaller, upright image.

2. Images formed by concave mirrors converge light and produce an upright, magnified

image if close and an inverted, smaller image if far away.

3. Convex and concave images are the same because they are formed by the reflection of

light.

4. In a plane mirror you see a left to right, virtual image, that is right side up. Plane mirrors

form virtual images, and curved mirrors can form both real and virtual images.

5.

6.

T. leads whole class

discussion. S. share findings

from lab activities.

T. shows Power Point with key

concepts and explanations.

S. revise initial predictions

based on their lab findings and

whole class explanations (on

original before and after

worksheet).

Assessment

Plan:

1. What kind of images are formed by convex mirrors?

2. What kind of images are formed by concave mirrors?

3. Compare and contrast images formed by concave mirrors, convex mirrors, and plane mirrors.

4. Draw a ray diagram to show the kind, size, and orientation of an image formed by a concave

mirror.

5. Draw a ray diagram to show the kind, size and orientation of an image formed by a convex

mirror.


Questions Predict (Before) Explain (After)

1. What kinds of

images are formed by convex mirrors?

2. What kinds of

images are formed by concave mirrors?

3. How are the images the same or different?

4. How do the images compare with those formed by plane mirrors?

5. How does the distance of the object from


Convex and Concave Mirrors Activities (Science Teacher’s Activities A Day – Internet Excerpt)

Mirrors can be flat or curved. When you see your image in a flat mirror, it is not distorted. When you look at your image

in a curved mirror, light rays leave the mirror at a different angle from the approaching rays, so distortions result. Mirrors

can be curved either inward or outward. Concave mirrors curve inward, like the interior of a bowl. Makeup mirrors are

concave mirrors because they enlarge the image. Mirrors that curve or bulge outward are called convex mirrors. This type

of mirror gives a wide field of view and is used in security mirrors in stores as well as the side mirror on cars and trucks.

the mirrors affect the characteristics of the image: upside down, right to left, small to large?

6. How do you think you would draw a ray diagram to show the image formed by the mirror in this diagram?

7. How do you think you would draw a ray diagram to show the image formed by the mirror in this diagram?


In this activity you will use the opposite sides of a shiny spoon to compare the images produced by concave and convex

mirrors.


Lab Activity 1 - Observing Images Produced by a Shiny Spoon

Materials

Shiny spoon

Sharpened pencil

Activity

4. Pick up the spoon by its handle and hold it so you are looking at the caved-in or hollowed-out side. You are looking into a concave

mirror. Describe the appearance of your image in the mirror. (Consider these characteristics in your description of the image: size,

clarity, upright/upside down, left/right orientation.)

5. With the spoon held at a distance from your face, move a pencil point slowly from your face toward the bowl of the spoon. Describe

how the appearance of the pencil point changes as it moves closer to the bowl of the spoon.

6. Turn the spoon around so you are looking at the back side of the bowl. You are looking at a convex mirror. Describe the appearance of

your image in the mirror. (Consider these characteristics in your description of the image: size, clarity, upright/upside down,

left/right orientation.)

7. Repeat the same process with the pencil point as you did with the concave side of the spoon on the convex side of the spoon. Describe

how the appearance of the pencil point changes as it moves closer to the bowl of the spoon.


Summary of your Lab Activity with Spoons

Fill in the Venn diagram below summarizing the similarities and differences you observed during your activity with the spoons

and your image and the image of the pencil. As you fill in your diagram consider these questions:

1. How did your appearance differ when you looked at the concave and convex sides of the spoon?

2. How did the appearance of the pencil point change as you moved it toward the spoon?

3. Which side was inverted at one point and right side up at another point?

4. Which side magnified the image?


Answers

1. Answers will vary, but most students will indicate their image was upside down in the concave side and right side up in the convex side.


2. As you moved the pencil toward the concave side of the spoon, the image started out upside down, but eventually flipped right side up

and was enlarged. In the convex side of the spoon, the image of the pencil point remained right side up as you moved forward, but it did

not enlarge as you got closer to the spoon.

This is a modification of an excerpted from: The Science Teacher's Activity-A-Day

http://www.amazon.com/gp/product/0470408812?ie=UTF8&linkCode=xm2&camp=1789&creativeASIN=0470408812



Lab Activity 2 - Concave Mirrors & Convex Mirrors

Concave Mirror Data and Observations

1. Using a very distant light source, determine the focal length of the concave mirror. Record the value here: _f =_______

2. Calculate the distance to the center of curvature, C, from the mirror’s surface. Record this distance, R, here: R =________

3. At your table, move the mirror so that the object distance meets each of the criteria in the table below. For each object distance,

experimentally determine the image distance and image height. The object is the light bulb and the object height is ho =_________.

4. Calculate the magnification for each image; the product of the object distance and image distance, and the sum of the image distance plus the

object distance to complete the table.

5. On graph paper (or on a computer-generated graph), plot the product, dodi, versus the sum, di + do, and find the slope of the line of best fit.

Remember to include units. Record the slope here: ____________. Compare the value to your focal length in 1.

Position of object

do (cm)

di (cm)

hi (cm)

M

Orientation (Upright or Inverted)

Type of Image (Real or Virtual)

dodi (cm2)

(di + do) (cm)

3F

Between 2F and 3F

At 2F

At 1.75 F

At 1.50 F

At F


At 0.50 F

Convex Mirrors – Data and Observations

1. Using a very distant light source, determine the focal length of the convex lens. Record the value here: _f =_______

2. Calculate the distance to 2F from the mirror’s surface. Record this distance =________

3. At your table, move the lens so that the object distance meets each of the criteria in the table below. For each object distance, experimentally

determine the image distance and image height. The object is the light bulb and the object height is ho =_________.

4. Calculate the magnification for each image; the product of the object distance and image distance, and the sum of the image distance plus the

object distance to complete the table.

5. On graph paper (or on a computer-generated graph), plot the product, dodi, versus the sum, di + do, and find the slope of the line of best fit.

Remember to include units. Record the slope here: ____________. Compare the value to your focal length in 1.

Position of object

do (cm)

di (cm)

hi (cm)

M

Orientation (Upright or Inverted)

Type of Image (Real or Virtual)

dodi (cm2)

(di + do) (cm)

3F

Between 2F and 3F

At 2F

At 1.75 F

At 1.50 F


At F

At 0.50 F

Resources:

http://boomeria.org/physicstextbook/ch13.html

Lab Activity 3 – Convex & Concave Mirror Simulation Ray Diagrams

Directions:

1. Go to this site on the internet.


2. Work through the following settings on the simulation.

3. Record your observations, diagrams, and reflections in the space below each section.

4. Before you begin this activity, take some time practicing how to use the simulation.

http://boomeria.org/physicstextbook/ch13.html



On the simulation, place the object within the focal length at 1.0 cm. Set radius of curvature to 4.05. Draw the rays and fill in the box to the right.

On the simulation, place the object within the focal length at 1.55 cm. Curvature remains at 4.05. Draw the rays and fill in the box to the right.


Virtual Right side up Magnified

Real Upside down Smaller






On the simulation, place the object within the focal length at 1.0 cm. Set radius of curvature to 4.05. Draw the rays and fill in the box to the right.









Circle the characteristics of your

images in the boxes below.