Laser Reflection Gizmo Answer Key

Name: Melvin Dudley Date: 04-25-2022 Student Exploration: Laser Reflection Directions: Follow the instructions to go through the simulation. Respond to the questions and prompts in the orange boxes. Vocabulary: angle of incidence, angle of reflection, laser, law of reflection, plane mirror, reflection Prior Knowledge Questions (Do these BEFORE using the Gizmo.) Imagine you shine a flashlight directly at a mirror, as shown below. ✏️ 1. Click the image, click Edit Draw an arrow showing the direction you think the beam of light will most likely reflect off the mirror. ✏️ 2. Click the image, click Edit Suppose you tilt the mirror. Draw an arrow showing the direction the beam will most likely reflect off the mirror now. Gizmo Warm-up Flashlights produce wide beams of light that have various wavelengths. A laser, on the other hand, is a narrow beam of light with only one wavelength. All the waves in a laser beam are parallel to one another. As a result, lasers are ideal for studying reflection, or how waves bounce off a surface. Using the Laser Reflection Gizmo, you can adjust the position of a laser beam and mirror to study how light behaves when it is reflected. 1. Drag the Angle slider back and forth. Describe what happens to the reflected laser beam: The laser beam reflects at a varied angle depending on how far the angle slider is adjusted back and forth. The laser beam is reflected at a negative angle when the angle slider is moved to the left, and at a positive angle when the slider is pushed to the right. 2. Drag the laser up and down. Describe what happens to the reflected laser beam: The laser's reflection point moves when the laser is moved up and down. Get the Gizmo ready: Activity A: Reflection from a plane mirror ● Set the Laser location to 0 cm. ● Set the Angle to 25 degrees. ● Make sure Plane mirror is selected. Introduction: A plane mirror is a perfectly flat, smooth surface. In this activity, you will study how plane mirrors reflect light. Question: How does the angle of a mirror determine the angle of the reflected light? 1. Observe: Turn on Show normal. The normal is the dotted line perpendicular to the mirror. The angle of incidence (θi) is the angle between the incoming laser beam and the normal. The angle of reflection (θr) is the angle between the reflected laser beam and the normal. Move the Angle slider back and forth. What do you notice about the sizes of θi and θr? When the angle slider is moved back and forth the sizes of arealways the same size as each other. grow and shrink, but they 2. Measure: Set the Angle to 40 degrees and turn on Show protractor. Each marking on the protractor represents 10 degrees. What do θi and θr equal? θi = θr = 3. Make a rule: What is the relationship between θi and θr? Turn on Show angles and move the Angle slider back and forth. Was your rule correct? My rule was accurate, therefore yes. The law of reflection states that the angle of incidence is equal to the angle of reflection. 4. Gather data: Use the Gizmo to complete the table below. Mirror angle 0° Angle of incidence (θi) Angle of reflection (θr) 25° 50° 5. Make a rule: How is the mirror angle related to the angles of incidence and reflection? The angles of incidence and reflection coincide with the mirror angle. Activity B: Reflection from non-planar mirrors Get the Gizmo ready: ● Turn off Show normal and Show protractor. ● Set the mirror Angle to 50°. Question: How can you use the angle of refraction to determine the shape of a non-planar mirror’s surface? 1. Observe: Turn on Insert beam splitter. How do the seven incoming beams compare with one another? How do the reflected beams compare with one another? All seven of the incoming beams are equally spaced apart, as are all seven of the reflected rays. 2. Observe: From the dropdown menu at lower right, select Mirror 1. Unlike the plane mirror, mirror 1 is not flat. A. Describe how the laser beams changed: The distance between the lasers has changed, as have the angles at which they reflect. B. Why do you think this happened? This occurred as a result of the mirror's uneven surface. 3. Solve: Turn off Insert beam splitter. Set the mirror’s Angle to 0 degrees and the Laser location to 35 cm. Check that Show angles is on. A. What are the angle of incidence and angle of reflection (θi and θr)? The angle of incidence and angle of reflection are both B. What does this tell you about the surface of the mirror in this location? This indicates that the mirror's surface is inclined downward where it is. C. Move the Laser location to 14 cm. How did the orientation of the beam change? Now the beam has been upwardly reflected. D. What does this tell you about the surface of the mirror in this location? This indicates that the mirror's surface is tilted up in this area. 4. Summarize: What does it mean if the reflected beam is above the incident beam? What does it mean if the reflected beam is below the incident beam? If the reflected beam is higher than the incident beam, it is reflecting off of an upwardly sloped surface, and if it is lower than the incident beam, it is reflecting off of a downwardly angled surface. 5. Collect data: You will now use the laser to map the surfaces of mirrors 1, 2, and 3. In the rows of the table, record each mirror’s angle at all the listed locations. If the beam is deflected downward, the angle is negative. Otherwise the angle is positive. Height Mirror 1 Angle Mirror 2 Angle Mirror 3 Angle 35 cm -3.5 3.8 0 30 cm -5 2.5 5 25 cm -3.5 1.3 0 20 cm 0 0 -5 15 cm 3.5 -1.3 0 10 cm 5 -2.5 5 5 cm 3.5 -3.8 0 0 cm 0 -5 -5 -5 cm -3.5 -3.8 0 -10 cm -5 -2.5 5 -15 cm -3.5 -1.3 0 -20 cm 0 0 -5 -25 cm -3.5 -1.3 0 -30 cm -5 -2.5 5 -35 cm -3.5 -3.8 0 ✏️ 6. Draw: Click the image, click Edit Use the data you collected to create drawings of the mirrors’ surfaces in the boxes below. Be sure to pay attention to negative signs, which indicate the direction of the angle. Mirror 1 Mirror 2 Mirror 3 7. Analyze: Does the law of reflection hold true for mirrors that aren’t flat? Use the Gizmo to explore this question, and describe your findings. Yes, non-flat mirrors are still subject to the law of reflection. Even if the mirror is curved, the point at which the laser hits it and reflects off of it is flat because the laser hits the mirror at such a small spot.