Exam (elaborations) GIZMOS Student Exploration Ray Tracing

Exam (elaborations) GIZMOS Student Exploration Ray Tracing Vocabulary: angle of incidence, angle of refraction, frequency, index of refraction, medium, refraction, Snell’s law, total internal reflection, wave front, wavelength, wave speed Prior Knowledge Questions (Do these BEFORE using the Gizmo.) Two runners ran side by side, each holding one end of a horizontal pole. 1. What would most likely happen if one of the runners began jogging in knee-deep water? The runner would start to feel a force that is causing his feet to fatigue a lot faster than running on land since the water is making his feet put more force to run 2. How would this affect the direction of the runners? Explain. The direction of the runner will move closer to (the normal) which will obviously not be visible without a diagram. The degree to which the runner was running in on land will now become smaller, making the runner run in a different direction. Gizmo Warm-up Light can travel through many materials, or media. As with a runner on pavement or sand, the speed of light can change when it moves into a different medium. The Refraction Gizmo allows you to observe what happens to a beam of light as it travels from one medium to another. Turn off View wave fronts. Set Index of refraction 2 to 3.0. 1. Click Play ( ). Observe the ray of light as it passes from Medium 1 to Medium 2. A. What happens to the speed of the light wave? The speed of the wave decreases in speed after it passes through the second medium. B. What happens to the direction of the light wave? The direction of the wave gets closer to the normal. The bending of the light ray you see is called refraction. 2. Click Reset ( ) and turn on View wave fronts. A wave front is an imaginary line that connects the crests or troughs of a wave. The wavelength of a wave is the distance between wave fronts. Reproduction for educational use only. Public sharing or posting prohibited. © 2020 ExploreLearning™ All rights reserved This study source was downloaded by from CourseH on :26:40 GMT -05:00 This study resource was shared via CourseH GIZMOS Student Exploration Refraction Click Play. What happens to the wavelength of the wave as it passes into Medium 2? The wavelength gets smaller as the waves pass through the second medium. Activity A: Angle of refraction Get the Gizmo ready: ● Click Reset. Turn off View wave fronts. ● Make sure View normal is selected. ● Make sure Index of refraction 1 is 1.0 and Angle of incidence is 45°. ● Set Index of refraction 2 to 2.0. Introduction: The normal is an imaginary line perpendicular to the boundary between two media. The angle of incidence is the angle between the light ray in medium 1 and the normal. The angle of refraction is the angle between the ray in medium 2 and the normal. ° Question: What affects how much light waves refract? 1. Measure: Click Play. To measure the angle of refraction, turn on Click to measure angles. Drag the protractor’s vertex to the intersection of the ray and the normal. Align the protractor’s legs to the ray and the normal in Medium 2. What is the angle of refraction? 20° 2. Gather data: For each angle of incidence listed in the table below, use the Gizmo to find the angle of refraction. Then, fill in the “Change of direction” column by subtracting the angle of refraction from the angle of incidence. Angle of incidence Angle of refraction Change in direction 20° 10° Closer to the axis of symmetry 40° 20° Closer to the axis of symmetry 60° 25° Closer to the axis of symmetry 80° 30° Closer to the axis of symmetry 3. Analyze: What patterns do you notice? Every time the refracted ray is always closer to the axis of symmetry but the larger the angle of incidence, the larger the angle of refraction. 4. Explain: Do you think refraction would occur if the angle of incidence is 0°? Explain. Reproduction for educational use only. Public sharing or posting prohibited. © 2020 ExploreLearning™ All rights reserved This study source was downloaded by from CourseH on :26:40 GMT -05:00 This study resource was shared via CourseH No, because it is a rule that when the incidence ray passes through the second medium at an angle of 0° or straight through the normal, there will be no refraction because the ray will go through the second medium without refracting. Reproduction for educational use only. Public sharing or posting prohibited. © 2020 ExploreLearning™ All rights reserved This study source was downloaded by from CourseH on :26:40 GMT -05:00 This study resource was shared via CourseH 5. Predict: The index of refraction indicates how fast light can travel through a medium. The higher the index is for a medium, the slower light will travel through that medium. How do you think increasing a medium’s index of refraction might affect the angle of refraction? If light travels, enter a substance with a lower refractive index (such as from water into air) it speeds up. The light bends away from the normal line. A higher refractive index shows that light will slow down and change direction more as it enters the substance. 6. Gather data: Keep the Index of refraction 1 set to 1.0. Set the Angle of incidence to 60°. For each Index of refraction 2 listed in the table below, use the Gizmo to find the angle of refraction and the change in direction. Index of refraction 2 Angle of refraction Change in direction 1.0 60° No change in direction 2.0 25° Closer to the axis of symmetry 3.0 15° Closer to the axis of symmetry 7. Analyze: What patterns do you notice? I noticed that the higher the index of refraction the lower the angle of refraction. 8. Explain: Why does no refraction occur when the media have the same index of refraction? If the refractive index is the same, there is no reason for the light to bend. Light will not spontaneously turn direction for no reason. The reason that light bends, or refracts, when it goes from one medium to another is because the light changes speed. 9. Explore: Set the Index of refraction 2 to 1.0. Set the Angle of incidence to 25°. Collect data for each Index of refraction 1 listed in the table below. Index of refraction 1 Angle of refraction Change in direction 1.5 40° Further away from the axis of symmetry 2.0 60° 3.0 N/A 10. Analyze: What did you notice about the change in direction in the first two trials? I noticed that the larger the index of refraction 1, the larger the angle of refraction. What happened in the third trial? Reproduction for educational use only. Public sharing or posting prohibited. © 2020 ExploreLearning™ All rights reserved This study source was downloaded by from CourseH on :26:40 GMT -05:00 This study resource was shared via CourseH There was no refraction, instead the ray reflected off the principal axis. When the angle of refraction is greater than 90°, the beam of light will reflect off of the surface instead of refracting through the surface. This is called total internal reflection.