Official Documentation of Investigation. Completed By. (Student Name) Pre-Read

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Justina Mason
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1 Official Documentation of Investigation Completed By (Student Name) Pre-Read When light waves hit a material, they cause the atoms (specifically, the electrons in metals) to oscillate (move back and forth). These oscillations cause the atoms to radiate a small wave back out in all directions. The reflected waves of many atoms combine to form a visible reflection. In the case of metals, the electrons in the atom's outer shell (farthest from the central nucleus) are not attached to the atom; they are free to move throughout the metal with very little resistance. When light shines on metal, it makes these free electrons oscillate or vibrate and the energy reflected is visible light. A mirror is mostly made of glass, but it also has a thin metallic film on the back side. It is that metallic film that reflects the light passing through the glass. The glass is only there to hold up the very thin film. Light Maze: What to Do: Your job is to apply the Law of Reflection to design a laser maze that reflects the laser beam through obstacles and ultimately projected on the target screen. You can work by yourself or in groups of up to 4. Each student is responsible for completing their own investigation document. Engage How to make patterns with laser light and mirror? Explore/Plan Using the image below and a straight edge, determine the placement of the laser by modelling the path light would travel if reflected off the center of both mirrors. HINT: First draw lines connecting the center of both mirrors. Next draw all reflections (remember, the angle of incidence = angle of reflection.) Finally, label a theoretically possible laser starting point (with a star). Commented [C1]: I think this was a good preread assignment that connects Matter and Interactions to Waves. Next time I assign this lesson I need to do a better job emphasizing the interconnectedness of the content. Also, students need to explain the key vocab in their own words. Specifically: Oscillate, vibrate, reflect, radiate, atomic composition, energy. Students need to make connections between these words, past content, and their own life experience. Commented [C2]: Next time have students come up with a list of things that could be done to make the project better: Example: Hot glue vs. play-doh for mirror supports. Compass vs. protractor. Basic logistics of what was challenging and practical solutions. Students must asses the goals of the project and determine the best way to complete the challenge. This is an essential skill. Commented [C3]: The center of the mirror is the point where the dashed line touches the surface of the rectangle. Many students misunderstood the directions and connected dashed line incorrectly. This explore activity is an opportunity to demonstrate the importance of using a STRAIGHT EDGE or RULER with PRECISSION. Many students intuitively understood the law of reflection, but I think students should not be expected to complete this activity without a solid understanding of the Law of Reflection. I prepped students for this activity using PhET Bending Light and taught them that angle in equals angle out for reflective surfaces. Later in this lesson I taught them specifically angle of incidence/reflection.

2 Explain/Model Drawing At the point of incidence where the ray strikes the mirror, a line can be drawn perpendicular to the surface of the mirror. This line is known as a normal line (labeled N in the diagram). The normal line divides the angle between the incident ray and the reflected ray into two equal angles. The angle between the incident ray and the normal is known as the angle of incidence. The angle between the reflected ray and the normal is known as the angle of reflection. USE A PROTRACTOR TO COMPLETE THE FOLLOWING TABLE (BASED ON MODEL BELOW) Hint: Draw a line connecting the center of Mirror 1 and 2. You need to determine the θ incidence and θ reflection angles. Notice, these angles are measured relative to the Normal Line. The normal line is drawn perpendicular to the surface at the point on a mirror that is reflecting light. Notice, the angle of incidence = angle of reflection. Repeat this process for each mirror to complete the table. Commented [C4]: Again, this activity should be modelled by the teacher at least for the first mirror. Some students were very confused with the expectations. Students were able to complete this section after teacher model. An extension to this portion of the assignment is to show the reflected rays and draw additional mirrors to serve specific purposes. Scenario Angle of Incidence Angle of Reflection An incident ray shines at the center of Mirror 1 and is reflected to the center of Mirror 2. An incident ray shines at the center of Mirror 1 and is reflected to the center of Mirror 3. An incident ray shines at the center of Mirror 1 and is reflected to the center of Mirror 4. Mirror 2 Mirror 3 Mirror 4 Mirror 1

3 Elaborate/ Extend and explain Laser Maze Materials * 1. You will receive 5 mirrors (small circular, or small square) 2. ½ Cup of Play-doh (mirror supports, use wisely) 3. ½ piece of cardstock, (can be cut into strips and used as supports for mirrors) 4. 1 glass obstacle 5. Ruler 6. Protractor 7. Screen to project on to *Additional Materials May Be Provided at TEACHER s Discretion This activity is an opportunity to extend theoretical understanding of light reflection. Science is more enjoyable HANDS ON, but student s respect, responsibility, and readiness is paramount. This activity can be completed entirely on paper using what you have already discovered about Mirrors, Angle of Incidence, and Angle of Reflection. Enjoy hands, but if you can t handle it CLICK HERE; The tech based lesson will require you to draw the same models (see following pages for each level) Commented [C5]: Before completing this lesson safety must be addressed. Students do not understand the dangers of laser pointers. Before starting this lesson I had students complete a Do Now that asked them to evaluate the risk of causing damage with a laser pointer based on the color of emitted light. Students were shown a chart of the visible light spectrum (including wavelength and frequency data.) Students should demonstrate an understanding of wavelength and frequency and their relationships to relative energy. The punchline of the do now review was Yes, red is less dangerous than violet but if I see you use the laser inappropriately once YOU ARE DONE!. I reminded students that hands on was a privilege and that the lesson can be completed entirely without a laser. The maze can be evaluated based on SCALE DRAWINGS alone. It is easy to tell if a students map (maze layout) will work. The laser pointers were only distributed to students whose layouts were carefully planned and drawn (using rulers and protractors).

4 Basic Challenge Set up three mirrors so that a laser is reflected off of each and lands in the Target zone of your screen. Once your set up is successfully projecting on the Target Zone, create a scaled diagram showing 1. Laser starting point and Finish Point 2. distances between mirrors 3. Normal line for each mirror 4. Angle of incidence and reflection for each mirror MODEL DRAWING Commented [C6]: Before students completed their own drawings I had a do now that showed a 2-dimensional layout of light bouncing and reflecting off of several mirrors. I had them practice planning the path that light travelled by adding additional mirrors to the provided drawing. To demonstrate proof of concept and excite students about the project, I projected the image on the board and allowed students fasten real mirrors on top of the theoretical mirrors. We tested the light maze (large scale whole class demonstration). Students were reminded about the importance of precision in their drawings as they would place their mirrors (small tile size) on top of their scale drawing just as we did using the projector. FIGURE 1

5 Above Basic Challenge Set up 5 mirrors so that a laser is reflected off of each and lands in the Target zone of your screen. Once your set up is successfully projecting on the Target Zone, create a scaled diagram showing 1. Laser starting point and Finish Point 2. distances between mirrors 3. Normal line for each mirror 4. Angle of incidence and reflection for each mirror MODEL DRAWING Figure 2

6 Junior Varsity Challenge Addition of prism. Set up 5 mirrors so that a laser is reflected off of each and lands in the Target zone of your screen. Note: The laser must past through the obstacle. The behavior of the light might depend on the type of obstacle you receive. Once your set up is successfully projecting on the Target Zone, create a scaled diagram showing 1. Laser starting point and Finish Point 2. distances between mirrors 3. Normal line for each mirror 4. Angle of incidence and reflection for each mirror MODEL DRAWING Figure 3

7 Evaluate Consider the diagram at the right. 1. Which one of the angles (A, B, C, or D) is the angle of incidence? 2. Which one of the angles (A, B, C, or D) is the angle of reflection? 3. Using Diagram Below. A ray of light is incident towards a plane mirror at an angle of 30-degrees with the mirror surface. What will be the angle of reflection? Answer 4. A ray of light is approaching a set of three mirrors as shown in the diagram. The light ray is approaching the first mirror at an angle of 45-degrees with the mirror surface. Trace the path of the light ray as it bounces off the mirror. Continue tracing the ray until it finally exits from the mirror system. How many times will the ray reflect before it finally exits? Answer: 5. What color is a mirror? Explain your answer in at least 3 sentences using examples, scientific vocab, and in a way that makes it very easy for me to determine your level of understanding Commented [C7]: Emphasize Essential Question Prior to Starting Lesson: What color is a mirror 6. Extension Questions: Why can t you see the path of a laser pointer through the air? Are there situations are scenarios that allow you to see the path of laser through the air? What happens when you shine a laser on projector screen? ipad Screen? Computer Screen? Flat screen TV? Some of the results may surprise you. Why do you think this happens? HINT: LIGHT CAN BE REFLECTED, TRANSMITTED, ABSORBED

Light and refractive index

$Light and refractive index$ 17 Fig. 7.1 shows a ray of light incident on a rectangular glass block at point X. W P X air glass Q R S Fig. 7.1 The ray of light is refracted at X. On Fig. 7.1, (a) draw the normal at X, [1] (b) draw