Mirrors and lenses are a student favorite! They are present everywhere and are a source of nearly endless intrigue. A unit on ray optics gives students an ability to understand them and their use. And part of that understanding involves understanding how and why the characteristics of the image that they see in a curved mirror or lens depends upon the location of the object. In the case of converging lenses, the image is sometimes upright and sometimes inverted, sometimes magnified and sometimes reduced in size, sometimes located on the oppositie side of the lens and sometimes on the same side of the lens as the object. Discerning how the location of the object affects the image characteristics is the topic of this Concept Builder.

Each question in the Concept Builder presents students with a lens, a principal axis, and an object arrow. Students must identify the characteristics of the image. They do so by tapping in one of the regions or locations outlined by a dashed rectangle; that selects the image location and orientation. They can then tap multiple times in that rectangle to toggle through the set of three possible sizes. Finally, they tap on the text field below the lens to identify the type of images as being real or virtual. We have come to describe these four characteristics of images using the mnemonic LOST. The L is for location. The O is for orientation (upright or inverted). The S is for relative size (smaller, larger, or the same size as the object). And the T is for type (real or virtual). Our Tutorial pages on the topic are great preparations for this activity. We believe that a hands-on lab is an essential pre-cursor to this activity. Other great resources can be found in the Resources section below that supplement the use of this Concept Builder.

The Concept Builder includes four Question Groups with two questions in each group. If a student misses a question from a Question Group, the other question will eventually be presented to them. The paired questions in each Question Group are different only in terms of which side of the lens that the red arrow object is on.

This Concept Builder was intended as an in-class activity. After some early lab investigation, some discussion and demonstrations of refraction, allow students an opportunity to interact with the questions.  In order to complete the activity, a student must correctly analyze each Question Group. If a student's analysis is incorrect, then the student will have to correctly analyze the same or very similar question twice in order to successfully complete the activity. This approach provides the student extra practice on questions for which they exhibited difficulty. As a student progresses through the activity, a system of stars and other indicators are used to indicate progress on the level. A star is an indicator of correctly analyzing the question. Once a star is earned, that question is removed from the que of questions to be analyzed. Each situation is color-coded with either a yellow or a red box. A red box indicates that the student has incorrectly analyzed the question and will have to correctly analyze it twice before earning a star. A yellow box is an indicator that the question must be correctly analyzed one time in order to earn a star. Once every question of a difficulty level has been analyzed, the student earns a trophy which is displayed on the Main Menu. This system of stars and trophies allows a teacher to easily check-off student progress or offer credit for completing assigned levels.

The most valuable (and most overlooked) aspect of this Concept Builder is the Help Me! feature. Each question group is accompanied by a Help page that discusses the specifics of the question. This Help feature transforms the activity from a question-answering activity into a concept-building activity. The student who takes the time to use the Help pages can be transformed from a guesser to a learner and from an unsure student to a confident student. The "meat and potatoes" of the Help pages are in the sections titled "How to Think About This Situation:" Students need to be encouraged by teachers to use the Help Me! button and to read this section of the page. A student that takes time to reflect upon how they are answering the question and how an expert would think about the situation can transform their naivete into expertise. 

 

 

There are a few resources at The Physics Classroom website that serve as very complementary supports for The L•O•S•T Art of Image Description (Converging Lens) Concept Builder. These include:
 

• Reading:
  Most students will find that  Lesson 5 of the Refraction and the Ray Model of Light Chapter of the Tutorial is a perfect accompaniment to this Concept Builder. In particular, the following two pages will be most helpful:
  
  Converging Lenses - Ray Diagrams
  
  Converging Lenses - Objecti-Image Relationships
  
  
   
• Curriculum Corner
  The Curriculum Corner section of our website contains a complete course curriculum that coordinates with our Tutorial section and our Minds On Physics program. There are a few activities in the Refraction and Lenses section that would be useful complements to this activity. These include:
  
  Lenses
  
  Ray Diagrams for Converging Lenses
  
  Visit Refraction and Lenses section of the Curriculum Corner.
  
  
   

• Minds On Physics Internet Modules:
  The Minds On Physics Internet Modules include a collection of interactive questioning modules that help learners assess their understanding of physics concepts and solidify those understandings by answering questions that require higher-order thinking. Assignments RL8 and RL9 of the Refraction and Lenses module are great complements to this Concept Builder. It is best used in the middle to later stages of the learning cycle. Visit the Minds On Physics Internet Modules.
  
  Users may find that the App version of Minds On Physics works best on their devices. The App Version can be found at the Minds On Physics the App section of our website. The Reflection and Mirrors module can be found on Part 6 of the six-part App series. Visit Minds On Physics the App.
  
  
   
• The Laboratory:
  There is no substitute for hands-on activities. And at The Physics Classroom, those hands-on activities can be found in The Laboratory section of the website. The following labs make useful pre-cursors to this Concept Builder.
  
  Exploring Lenses
  
  LOST Art of Image Description
  
  Lens Equation Lab
  
  Visit The Laboratory
  
   

Additional resources and ideas for incorporating The L•O•S•T Art of Image Description (Converging Lenses) Concept Builder into an instructional unit on Reflection and Mirrors can be found at the Teacher Toolkits section of The Physics Classroom website.  Visit Teacher Toolkits.