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.
Introduction
(Predict,
Explain)
Materials
Power point with
Images from plane,
concave, and
convex mirrors.
Instructional Sequence
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.
Teacher/Student
Actions
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
Display Mirror Mirage of Pig
Worksheet with
prediction
scenarios
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.
Like the Escher image the
mirage pig should provide
interest and motivation. T. also
lead discussion determine
vocabulary - Real vs Virtual
Joyce Lowry and Vicki Lewis
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://tutorhomework.com/
Physics_Help/len
s_ray_simulation.
html
Worksheet
Observe:
1.
2.
3.
Pass out lab activity questions/observation worksheet for each of the four labs.
Review safety rules (and if using glass mirrors, must wear goggles)
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.
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.
2.
3.
4.
Images formed by convex mirrors diverge light and produce a smaller, upright image.
Images formed by concave mirrors converge light and produce an upright, magnified
image if close and an inverted, smaller image if far away.
Convex and concave images are the same because they are formed by the reflection of
light.
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.
Assessment
Plan:
1.
2.
3.
4.
5.
What kind of images are formed by convex mirrors?
What kind of images are formed by concave mirrors?
Compare and contrast images formed by concave mirrors, convex mirrors, and plane mirrors.
Draw a ray diagram to show the kind, size, and orientation of an image formed by a concave
mirror.
Draw a ray diagram to show the kind, size and orientation of an image formed by a convex
mirror.
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).
Joyce Lowry and Vicki Lewis
Questions
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
Predict (Before)
Explain (After)
Joyce Lowry and Vicki Lewis
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?
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.
Joyce Lowry and Vicki Lewis
In this activity you will use the opposite sides of a shiny spoon to compare the images produced by concave and convex
mirrors.
Joyce Lowry and Vicki Lewis
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.
Joyce Lowry and Vicki Lewis
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?
Joyce Lowry and Vicki Lewis
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.
Joyce Lowry and Vicki Lewis
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
Joyce Lowry and Vicki Lewis
Joyce Lowry and Vicki Lewis
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
3F
Between 2F
and 3F
At 2F
At 1.75 F
At 1.50 F
At F
do
(cm)
di
(cm)
hi (cm)
M
Orientation
(Upright or
Inverted)
Type of
Image
(Real or
Virtual)
dodi (di +
(cm2) do)
(cm)
Joyce Lowry and Vicki Lewis
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
3F
Between
2F and
3F
At 2F
At 1.75 F
At 1.50 F
do (cm)
di
(cm)
hi (cm)
M
Orientation
(Upright or
Inverted)
Type of
Image
(Real or
Virtual)
dodi
(cm2)
(di + do)
(cm)
Joyce Lowry and Vicki Lewis
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.
http://tutor-homework.com/Physics_Help/lens_ray_simulation.html
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.
Joyce Lowry and Vicki Lewis
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.
Virtual
Right side up
Magnified
Real
Upside down
Smaller
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 1.55 cm. Curvature remains at 4.05. Draw the rays and fill in the box to the right.
Circle the characteristics of your
images in the boxes below.
Joyce Lowry and Vicki Lewis
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.
Virtual
Right side up
Magnified
Real
Upside down
Smaller
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 1.55 cm. Curvature remains at 4.05. Draw the rays and fill in the box to the right.