Absorption, Transmission, and Reflection: Creating Models
Lesson 3 of 7
Objective: Students will be able to provide evidence that demonstrates that waves are transmitted, absorbed, and reflected.
This lesson engages students in answering the NGSS essential question, "What are the characteristic properties of waves and how can they be used?". Specifically, this lesson focuses on MS-PS4-2, which states that students who demonstrate understanding can "develop and use a model to describe that waves are reflected, absorbed, and transmitted through various materials."
Moreover, this lesson emphasizes the science and engineering practice of developing and using models to describe phenomena (SP2).
In my experiences with students, I have found that demonstrating understanding is more than simply repeating a definition that has been provided. Real understanding occurs when a student can demonstrate and create their own connections to real world phenomena. This lesson allows students to do just that. It is a lesson that does not have one correct answer; each student's unique interpretation and application, as long as it is founded in evidence, can demonstrate mastery.
At the beginning of this unit, students are provided with their Unit Guide, which is the Essential Question of the unit along with the skills students are expected to master in the form of "I can" statements. At the beginning of the unit, students have rated themselves on a scale of 1 to 4 (4 representing sophisticated mastery and 1 representing a student just starting in their learning) for each of the "I can" statements or skills. Pre-assessment and self reflection is a key to this lesson.
Even if you do not use my Essential Question or "I can" statements, it will be important to have your students pre-assess their level of mastery in regards to the NGSS standard MS-PS4-2 prior to beginning the lesson.
To begin the class period, I begin with a quick formative assessment in order to collect data on the level of student mastery of a skill previously introduced. It is important that students complete formative assessments independently in order to collect accurate data on where each individual student is in their learning.
The formative assessment I give on this day deals with Skill 2 from the Unit Plan, "I can create a model that represents how the energy of a wave affects the amplitude." The formative assessment as well as some student examples are included in the resources below.
Prior to the next class, I sort these formative assessments into piles of common student learning. For example, there may be a group of students that have forgotten that diagrams should have a title and caption, a group that has shown understanding in energy/amplitude but not demonstrated the purpose in their model, and a group that has demonstrated a misconception that energy changes the frequency as opposed to the amplitude. The following class period, I will pull these groups of students to discuss and reteach the specific areas they are still working towards mastery on.
Students that demonstrate mastery indicate a positive linear relationship between energy and amplitude as well as draw a diagram that serves the purpose to demonstrate the relationship between energy and amplitude. One thing that I love about models is that students can demonstrate mastery in many ways. One student could show energy and amplitude using longitudinal waves while the other could chose transverse waves to model the relationship. The video below describes some aspects of student work that would demonstrate mastery as well as common misconceptions or challenges that students who have not mastered the material may face. This may help you identify groups you could sort and identify for mini lessons or reteaching in the following lesson.
One of the most important factors to the success of a lesson is that the students make connections to the skill that they are targeting. Each day, I begin my lesson by asking a student at random, "What are you going to be learning today?" At this point in the year, students know the importance of the Essential Question and where it is posted in my classroom. Students should respond something like, "I should be learning about the characteristic properties of waves and how they are used in the world."
I then have the students turn to the Unit Plan page in their binder. I ask the students to quietly and individually read Skill 4: I can provide evidence of reflection, absorption, and reflection in the world. This lesson is the first lesson relating to this skill. Each time I am about to introduce the first lesson of a skill I have the students take time to rank themselves on where they feel they are with the skill on a scale of 1 to 4 (4 representing mastery). After they self assess, I ask the students to take a minute silently to underline the key vocabulary in the skill that they think will be important to connect to in the lesson. I also have them circle the key verbs that explain what they will have to be able to do with that vocabulary.
After students have underlined the vocabulary and circled the important verbs, I randomly ask students to offer the vocabulary they should be connecting to in today's lesson. Students often say, "transmission, absorption, and reflection". I then ask the students what they should be able to "do" with that vocabulary. I might say, "Should I just be able to define it? How could I demonstrate understanding?". Students might respond, "I have to be able to provide evidence of those three things." At this point in the year after implementing scientific and engineering practices, students might also say, "I could provide evidence by creating a model or diagram." We then talk about how they should focus for opportunities to make connections to these vocabulary and evidence. We practice sharing with the class when we make connections to skills. For example, when I provide the definition of transmission later in the lesson, students should raise their hand. A student might say, "I made a connection to Skill 4 when you mentioned 'transmission'." Another student might follow up with the question, "How can you provide evidence of transmission?" (This takes practice! You need to take time to show them and model how to do this!) At the moment a student shares with the class their connection to the skill, many more students 'tune in' and try to make connections of their own.
I then provide the students with formal definitions of transmission, absorption, and reflection. The resource, "Teaching Points" is a guide I use to provide the definitions of transmission, reflection, and absorption as well as examples and teaching points I want to make. It is not something I give the students; however, I could see how it might be useful to do so in some cases. On a side note, the length of this section can vary greatly. I have found that when students really start connecting to what they are supposed to be demonstrating, they volunteer many examples from their own lives to add to the discussion. Sometimes, this mini lesson is extended 10 minutes due to students offering their own connections to the real world.
Break students up into groups of about 6 students. Have each group count off 1 - 6, reminding the students to remember their number. On the board, elmo, etc., write the following:
- Reflection of Light
- Absorption of Light
- Transmission of Light
- Reflection of Sound
- Absorption of Sound
- Transmission of Sound
Explain that models are an important method scientists (and students!) use to explain phenomena in the world. Today's focus is modeling evidence of the transmission, reflection, and absorption of waves. Let the students know that you will be giving their group a "Mystery Box" that contains various different objects and types of matter that they can utilize in creating their models. The boxes I prepared for the students included:
- A slinky
- A flashlight
- A laser pointer
- A straw
- A pencil
- A magnifying glass
- A ruler
- A mirror
- A tin baking dish with a transparent lid
- A tuning fork
- A shallow plastic dish (or refraction dish)
- Earmuffs or Headphones
- Colored film/tissue
- A prism
- A lens
- A cardboard box
I explain that student #1 would be using any of these materials to model reflection of light, #2 would be using the materials to model absorption of light, etc. Once each member of the group had identified a way they could model the wave behavior, each member would present to the small group their model. I emphasize that in addition to showing their model, they must describe the evidence they are seeing/hearing that proves the representation is in fact demonstrating that wave behavior.
Following each member of the group demonstrating their model, each member of the group must take on a new model. I explain that the student that had #1 Reflection of light now must model #2 Absorption of Light, the student that had #2 Absorption of Light must now model #3 Transmission of Light, and so on. The process repeats itself until all students have demonstrated all six models. One key note I make to my students is that they may not repeat a model that a student prior to them has already used for that model. However, the same materials could be used for more than one model. For example, the sunglasses could be used for absorption of light and reflection of light.
It is always amazing to me to watch the students develop their own models. When I put the materials in the box, I have my own preconceived ideas about what they will do with them. However, they always surprise me! Allowing students to have an open ended modeling experience in which there is not one right answer that allows them to attach their own unique vision to their understanding has proven to be very effective in my classroom.
Transmission of Sound: Here is a student modeling transmission of sound with a slinky. Notice that he explains that compressions are created by the sound and that he cites evidence that the sound is moving through the slinky.
Absorption of Sound: This student models absorption of sound by having another student put on headphones. Notice that she asks the student about the amplitude of her voice with and without the headphones to create clear comparison for evidence.
Transmission of Sound: When demonstrating, this student uses a tuning fork and aluminum pie tin to model transmission. Notice that he asks the students on the other side of the tin if they can hear/feel the vibrations and sound on the other side of the tin to serve as evidence of transmission.
The purpose of the student models was to identify evidence of transmission, reflection and absorption of waves. Thus, it is important that they connect to the similarities in evidence between sound and light waves. Though different types of waves, the evidence that is helpful in identifying each is similar. As a class, we brainstorm the type of evidence we would look for in a phenomena that would indicate that it is transmission, reflection, or absorption. On the board, elmo, chart paper, etc., write down the students ideas of evidence. Some examples students typically share are:
- Evidence of Reflection: You can see/hear the wave come back from the matter it hit on the same side as the disturbance.
- Evidence of Absorption: You can see/hear the wave "less" on the other side of the matter, specifically with light students mention that the object may get hot.
- Evidence of Transmission: You can see/hear the wave on the other side of the matter.
Prior to the end of the class period, I ask the students to rate themselves again on a scale of 1 to 4 on Skill 4: I can provide evidence of reflection, absorption, and reflection in the world.. We then discuss how the number changed from the beginning of the class to the end of the class and connect that growth to the idea that they knew what they were supposed to be learning and were able to make connections to the skill/learning target.