Teacher Notes for Reflection and Mirrors
Lesson Plans || Learning Outcomes and Activities || Teacher Notes || Labs
Unit Overview
We would suggest that 11 days on this topic would be necessary to cover all
Learning Outcomes. There are three primary goals:
- To understand why the reflection of light off a smooth, flat surface results in the formation of an image.
- To understand why the reflection of light off a concave or convex surface results in the formation of an image.
- To use qualitative and quantitative approaches to describe how the object distance affects the image characteristics for plane, concave, and convex mirror.
The first ~5 days is devoted to plane mirrors. The remaining time will be devoted to curved mirrors.
Time, Content, and Decisions
When it comes to planning all the Physics you wish to teach your students, time is more often the enemy than the friend. While it is difficult for us to imagine cutting anything out of a curriculum, the unfortunate reality is that there is a day on the school calendar that says Summer Break begins.
If you need to steal time from Mirrors to give time to another topic, we might suggest limiting the math at the end of the unit. We think the mirror equation is rather cool. Its ability to predict the same conclusions regarding image characteristics that students view in lab and the same conclusions regarding image characteristics that students learn from ray diagrams strikes us as downright groovy. But unfortunately, our giddy enthusiasm for the mirror equation has never been satisfactorily matched by students. So transfer some of those mirror equation days to doing more projectile problems (or the topic of your choosing) and we are certain you'll be quite satisfied.
Labs!!
This unit is as phenomenological as they come. Every outcome can begin with a lab or demonstration. The hands-on experiences do not require fancy equipment. We've suggested six labs. Our Teacher Guides suggest alternative methods. There's more lab ideas in our
Laboratory section.
Lasers
Many of our labs rely on the use of lasers. We are not referring to the multi-hundred dollar variety. We are referring to leveling lasers that can be purchased for a low cost at a hardware store. They are often a promotion at Menards and Home Depot on Black Friday. Do take the time to train students to use them with caution. Make a big deal of it. Lasers are not toys and should not be shined in another person's eyes.
The Honors Difference
We have followed a very similar unit plan for this Honors Physics course as we used for the
on-level Physics course. There have been only a few changes. First we suggested the
Improving Your Image Lab Test (see below) on Day 5. Second, we added a third mirror equation CalcPad problem set and sprinkled more difficult problems throughout all three problem sets. We also used a different Think Sheet for the topic:
Mirror Equation Problems. Third, we replaced the usual
Light Reflection Think Sheet with the
Firing My Laser Challenge. Fourth, we added the Magnification Ratio lab.
Finally, we've use two different Think Sheets for our plane mirror ray diagramming learning outcome:
Ray Diagrams for Plane Mirrors and
The 6-Foot Person Problem. Other additions that could be made are Right Angle Mirrors (see below) and Parallel Mirrors (see below).
Lab Test
We have suggested the
Improving Your Image Lab Test on Day 5. A Lab Test is like any test in that the teacher provides no hints, no advice, no direction, and no help. Student lab groups are 100% on their own to address the purpose of the lab.
All decisions are left to the lab groups. Lab groups cannot communicate with other lab groups; it is after all a "test". Use of a lab test provides the teacher a reasonably good assessment of where students are at with respect to solving a lab problem. We do recommend the following: Every student receives a copy of the
Lab Test and must complete it from beginning to end. Presumably members of the group will be working together on the test so all copies should reflect the group's thinking and decision-making. Collecting a copy from each group member insures that all members participate. Lab groups should be instructed to staple all the Lab Tests together with the one that is to be graded on the top. Grading just the top copy reduces the amount of grading. Quickly checking that all other copies are complete insures that all members of the group receive the same grade.
Right Angle Mirrors
Right angle mirrors can be an interesting topic for Honors Physics students. For an addition 1-2 days, you can add a lab experience, a reading assignment, and some ray diagramming on the topic.
Reading:
Physics Classroom Tutorial, Reflection and the Ray Model of Light: Lesson 1, Part e
Ray Diagrams: Question #14 from
Plane Mirror Images
Lab: Lab RM5 Right Angle Mirrors from the
Laboratory section. See
Teacher's Guide.
Parallel Mirror Challenge
Many students have likely observed situations in which there were parallel or near parallel mirrors. And object (like one of your students) standing between the mirrors can look into the mirrors and see what appears to be an infinite number of images extending into "infinity". Honors Physics students have the mathematical capabilities to figure this out. We invite you to try the
Infinity exercise with your students. Students determine the distances from the
rightmost mirror in a parallel mirror system to all the images located to the right of the mirror if an object is positioned
a cm from the left mirror and
b cm from the right mirror. Once they've determined some distance values they make an effort to generate an equation that expresses these distances as a function of
a and
b. It's a suitable challenge for most Honors Physics students.
Other Resources
There are a few resources that we did not list in our
Lesson Plans and
Learning Outcomes and Activities that you may find to be very helpful. These include:
- Science Reasoning Center: Curved Mirrors
Students analyze and interpret a complex diagram; identify the effect of variations in one quantity upon another quantity; draw conclusions that are supported by one or more data presentations; identify evidence that supports a conclusion; transform data from a table into a graph; and to interpolate and extrapolate from data in a table.
- Science Reasoning Center: Object-Image Relationships
Students identify the effect of one variable upon another variable; select values and compare values on a graph; draw conclusions that are consistent with a data presentation (or two); combine data from two graphs in order to identify an accurate conclusion; and to interpolate using values on a graph.
- Concept Builder: Law of Reflection
Students use the law of reflection to predict the direction that a light ray will reflect off a mirror if given the incident light ray.
Teacher Presentation Pack
We say this a lot. But we think it is worth saying. Our
Teacher Presentation Pack is a huge time-saver. For early-career and cross-over Physics teachers, it may also become a life saver. It includes a large collection of Slide Decks, animations, and graphics for use in your classroom. Once downloaded, you can modify and customize the Slide Decks as needed. The slides are highly organized and (mostly) graphical; they make great graphic organizers for any student, and especially for the struggling student.
Learn more.
Also Available ...
Physics teachers may find the following
for-sale tools to bes useful supplements to our Lesson Plan and Pacing Guide section:
- Task Tracker Subscription (annual purchase)
A subscription allows teachers to set up classes, add students, customize online assignments, view student progress/scores, and export student scores. Task Tracker accounts allow your students to begin assignments in class or at school and to finish them at home. View our Seat and Cost Calculator for pricing details.
- The Solutions Guide
We publish a free curriculum with >200 ready-to-use Think Sheets for developing physics concepts. The Solutions Guide is a download containing the source documents, PDFs of source documents, and answers/solutions in MS Word and PDF format. An expanded license agreement is included with the purchase. (Cost: $25 download)
- Teacher Presentation Pack
This is a large collection of downloadable content packed with nearly 190 Microsoft PowerPoint slide decks, the corresponding Lesson Notes (as PDF and fully-modifiable MS Word format), about 170 animations (in .gif, .png, and .mp4 file formats), a countless number of ready-to-use images (including the original source documents that would allow for easy modification of those images), and a license that allows teachers to modify and use all the content with their classes on password-protected sites (such as course management systems). (Cost: $40 download)
- Question Bank
We distribute a Question Bank that includes more than 9300 questions neatly organized according to topic. The Question Bank is the perfect tool for busy teachers or new teachers. Even if you don't use the website with your classes, the Question Bank will assist you in quickly putting together quizzes, tests and other documents with high-quality questions that target student's conceptions of physics principles. And if you do use The Physics Classroom website, the Question Bank is the perfect complement to the materials found at the website. (Cost: $25 download)