Engage: Broken and Squished?

This duck appears to be broken. Why is this happening?

can see half of the duck above water and other half below water. Top half of duck appears to not be attached to the bottom half of the duck.

Why does the image of the man on the back of this spoon appear squished?
 

Source: 
Duck: Courtesy of Allison Hope Nichols via Flickr Spoon: Courtesy of B Rosen via Flickr

Explore I: Lunch and Light Lines

Here are some college students waiting in a lunch line. None of them appear broken or distorted like the images of the man in the spoon and duck. What do you know about waiting in the lunch line? You usually have to be in one straight, single-file line, right? What about light? Does it travel in a straight line as well? Watch the video below. Think about what is happening and consider the following question: Does light travel in a straight line?

To Show that Light Travels in Straight Lines - YouTube.mp4

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Source: 
Courtesy of: https://www.youtube.com/watch?v=Hh4lregaYes

Explain I: Traveling Light Rays

As you saw in the three-hole investigation, light traveled in a straight line through each of the holes in the metal plates and appeared on the wooden end of the desk. If the light was able to go through the three holes and appear on the end of the desk, then lights rays must travel in a straight line. When the student moved the center plate, it blocked the light ray. Did you notice that the light ray did not change its path and move around the obstruction? This is because light travels in a straight line through the air unless acted on by another material, which scientists call a medium. In the case of this investigation the medium completely blocked the ray of light from going any further. Air, also a type of medium, allowed the light ray to travel through it. 

How is a lunch line at school similar to the way a light ray travels? Use the comparison document, RM-1 Comparing Lunch Lines and Light Rays, in the related items section below to record your thoughts.

Explore II: Media

In the last section, you saw that the metal plate blocked the light ray completely. What other media also block light rays?

Download the Media Testing activity sheet, RM-2, from the Related Items section below. This document will help you to test everyday objects in your home to determine what media do and do not block the path of light rays. Media is the plural form of medium.

Explain II: Three Basic Types of Media

Of the media you tested, which did not allow light to pass through?

Which medium allowed light to travel through it in a perfectly straight line? 
How do you know?

Into what categories did you sort the media?

Most scientists would sort these into three categories:

  1. Does not block the light
  2. Blocks some of the light
  3. Blocks all of the light

There are technical names for these, of course. 

Opaque (pronounced Oh-pake) describes a medium that blocks all of the light. Light rays cannot pass, or be transmitted, through these media. Opaque media include materials such as wood, cement, aluminum foil, and leather.

Translucent (pronounced Trans-loo-sent) describes a medium that blocks some of the light. Light rays can partially be transmitted through these media. Translucent media include materials such as waxed paper, frosted glass, muddy water, and milk.

Transparent (pronounced Trans-pair-ent) describes a medium that blocks very little to no light. Light rays can be easily transmitted through these media. Transparent media include materials such as plastic wrap, nonfrosted glass, water, and air. 

Explore III: Bouncing and Bending

We know that light travels in a straight line. What happens when light rays meet a particular type of opaque media, such as a mirror? Watch the video below to see what happens. Safety Note: Do not try this at home without proper eye protection

Green Laser Beam Reflecting from Mirrors - YouTube1.mp4

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Source: 
Video Courtesy of: https://www.youtube.com/watch?v=zNTP_x0bEBQ

Think about this question: Did the light rays travel through one medium or more than one medium? How do you know?

Now, watch this next video.

Bending a laser beam. Experiment. - YouTube1.mp4

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Source: 
https://www.youtube.com/watch?v=zTx7UoPXvr4

Now think about these questions:

  • Did the light rays travel through one medium or more than one medium? How do you know?
  • What happened to the light rays as they travelled?
  • How is the second video different from the first video?

Explain III: Reflection and Refraction

If you think about the two videos you just viewed, light can travel through one medium and bounce (reflect) off another medium, or it can travel through one medium and bend (refract) as it travels through another medium. The important thing to understand is whether the light rays bounce off the second medium or travel through it. If they bounce off the second medium, it is reflection. If they travel through the second medium, it is refraction. Don't forget that air is often the first medium!

We cannot see individual light rays with the naked eye. We know that light can travel through transparent and some translucent media based on the sorting activity in the last section. What we can see, however, is the effect of the bouncing or bending of light rays. In order for humans to see objects, light rays must bounce off objects and back to our eyes. Our eyes then use this information to create a picture of what is in front of us.

If refraction occurs, the light rays travel through a different medium and bend. When the light rays come back to your eye, they come back at a different angle. This can make the object appear distorted. Let's think about the image of the duck from the first section. The top of the duck is above the water. The light rays travel through the air, reflect off the duck, and bounce back to our eyes. Our eyes interpret this as a duck sitting on the water. Half of the duck is under the water. The light rays travel through the air, the glass of the tank that is holding the water, and the water. The light rays in this case are traveling through at least three types of media. This bending of the light rays creates the illusion that the duck is broken in half.

If reflection occurs on a flat surface, the light rays reflect back at the same angle and the object appears normal. If reflection occurs on a curved surface, the light rays still reflect, but they reflect back at a different angle. This type of reflection gives you an image that can be distorted or appear upside down. Students often mistake this type of reflection for refraction because the image appears distorted.

Why is reflection on a curved surface not the same as refraction?

The answer is that any time light rays travel through only one medium, in this case air, it is reflection. Light rays travel from the light source, through the air, hit the opaque spoon, and reflect back to our eyes to produce the image we see. Remember, when refraction happens, the light rays must travel through one medium (air) into another medium where the rays bend.

Elaborate: Using Refraction to Survive

Want to go fishing? Download RM-3 GoFish! from the Related Items section below. When you have finished the activity, click on the image of the heron below to make connections between your activity and this bird species.

What if you live below the water but have to think about refraction when you are hunting prey above the water? Watch the video below about the archer fish and how it uses refraction to its advantage.

Source: 
Photo courtesy of Davide Simonetti via Flickr

ArcherFish.mp4

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Source: 
Courtesy of Nat Geo Wild

Choose one of these organisms or another organism that uses reflection or refraction to survive and learn more about the organism. Create a short video commercial, pamphlet,or audio recording informing the public that science is everywhere. In your final product, be sure to share what you learned about the organism and and how it uses reflection/refraction to survive.

Teacher Notes

This resource is a compilation of text, videos, and other elements to create a scaffolded 5E learning experience for students. This is meant for Tier I instruction under the Response to Intervention (RtI) model for grade 5 science TEKS (6)(C). The resource scaffolds learning from initial concept of how light travels in a straight line, to the more complext topic of what materials can light travel through, and finally culminating in the concepts of reflection and refraction.

Be sure to check for prerequisite knowledge and skills as well as differentiation needs by reviewing the entire resource and the related items before assigning it to or working through it with your students.

This resource can be used for instruction in a variety of ways.
• Use with a single computer and projector; this resource can be delivered in a traditional classroom.
• Use with a combination of individual student computers and teacher computer and projector (in either a computer lab or other 1:1 environment).
• Assign the resource to students as work to do outside of the school day as part of a "flipped classroom" to allow application, practice, and additional support during the school day.
• Use with students as tutorials.
• Share with parents to inform them about what their child is learning in school.
• Use with students who are unable to participate in the traditional classroom environment.

Engage
Students observe images involving reflection and refraction. This gets students thinking about why distortion occurs.

Classroom Options
• Have students look at the images and do a think-pair-share. Have students record their thoughts in their science notebooks.
• Provide students with additional images that involve reflection and refraction. Have them sort the images into categories based on what they believe is causing the distortion of the image. Have students paste these images onto chart paper or sort electronically using the image files. Revisit these after the Explore/Explain III cycle to check for understanding and allow students to revise their initial thoughts.

Explore I
Students have the opportunity to experience light traveling in a straight line. Students start by thinking about a lunch line and how students travel in a lunch line. They transfer this thinking to watching a video of the three-hole investigation to test whether light travels in a straight line. A student narrates this video.

Classroom Options
• Have students conduct the investigation themselves before watching the video. Putting a Styrofoam cup upside down, cutting a slit in it, and inserting an index card will produce a setup similar to that in the video at minimal cost. Punch holes in the index cards to allow the light rays to travel. You will need to use a laser pointer for this investigation, so be sure to check your district policy on using laser pointers in the classroom and never allow students to aim the light at other students or look directly into the laser beam.

Explain I
The Explain makes the connection of light rays traveling in a straight line unless they are acted upon by something else. This something else is called a medium. Medium is specifically mentioned in the student expectation and is critical to students' later understanding of the essential difference between reflection and refraction. Air is the medium that most students forget because it cannot be seen. It is important to remind students that air is one of the major media that light travels through on Earth.

Classroom Options
• Allow students to work in pairs or small groups to complete their comparison document. This could also be done electronically using an interactive white board or an online bulletin board program.
• Do a knowledge check using a cloze passage and have students complete it as an exit ticket. Here's an example
o Light travels in a ____________ line. A _________ can allow light rays to travel or not allow them to travel. ____ is an example of a medium we cannot see that allows light to travel.

Explore/Explain II
The word media is used here as the plural form of medium. While students will likely not be tested on this specific vocabulary, it is still important to expose them to the vocabulary of the discipline. Students investigate different media they find around their home and test how much light travels through each type of medium. Students should understand the three major types of media: opaque, translucent, and transparent.
This investigation and discussion relate back to 5(5)(A) because students are classifying matter based on physical properties. Students cannot understand the next phase of the resource, dealing with reflection and refraction, unless they understand that there are media through which light can travel and media through which light cannot travel.

Classroom Options
• Create a “buffet” of materials for students to test. Allow groups to select up to six materials. When they have completed the investigation, allow students to have small-group  conversations (2–3 students) with other students who tested the same material but were not in their investigational group. Do this instead of the traditional investigational-group sharing. This mimics what scientists do in the real world and allows students to process their findings.
• Consider creating a realia wall with samples of these media and the categories into which they fit. It is a great visual for students to refer to as they continue the study of reflection and refraction.
• Take students on a scavenger hunt around the school with sticky notes and label things around the building that are transparent, translucent, and opaque. Bring black or dark-blue tablecloths that students can use as a tent in order to darken the location as they test with the flashlight.

Explore III
In the third and final Explore, students will observe in the first video how light behaves when it travels through one medium and, in the second video, how light behaves when it travels through more than one medium. If possible, pull up the resource side by side in two browser windows (not tabs) so that the teacher can pause each of the videos and allow students to see the difference in the behavior of the light rays.

Classroom Options
• Allow students to do these investigations themselves rather than watching the video, if possible. It also is possible to insert another investigation here that is hands-on and illustrates the difference between how light rays behave during reflection versus refraction. Again, if using laser pointers, ensure that the district/campus policy allows student use of these tools.
• Encourage students to draw in their science notebooks what is happening and to label the media involved. This will create yet another visual for students to connect with during Explain III.

Explain III
This is where the words reflection and refraction come in. At this point in this scaffolded student experience, students now understand light travels in a straight line unless acted upon by a medium; those media can be opaque, translucent, or transparent; and this property of matter affects whether the light rays can travel through the medium. Using this knowledge, students can understand that in the process of reflection, light rays traveling through only one medium can reflect off another medium. Students can now understand that in the process of refraction, light rays travel through one medium and through another medium, where the bending occurs. For fifth-grade students, this is the critical understanding, rather than reflection is bouncing and refraction is bending. Students should be able to look at any scenario and ask themselves if the light ray is traveling through one medium or more than one medium.
It is true that reflection and refraction occur at the same time. When we see the image of the duck, refraction and reflection are happening. We could not see the duck without the process of reflection. While many advanced fifth-graders may understand this and should be allowed to express that understanding, this duality is likely to be better understood by students with more mature cognitive ability in middle school and later in physics.

Elaborate
Here the students have an opportunity to engage in a hands-on experience with refraction. Students explore the great-billed heron and the archer fish. There are examples of how physical science applies to life science, increasing the relevance of 5(6)(C). What is important here is the application of a physical science concept to life science and understanding that science is not made up of clearly defined disciplines but an interconnected web of concepts.