Student Exploration: Laser Reflection

Student Exploration: Laser Reflection 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. Draw an arrow showing the direction you think the beam of light will most likely reflect off the mirror. 2. 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 reflects off in the direction of the tilt. If the mirror is tilted back, the laser reflects up, and vice versa. 2. Drag the laser up and down. Describe what happens to the reflected laser beam: The point where the laser is reflecting off of moves up and down, but the angle does not change. Activity A: Get the Gizmo ready: 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 (8) is the angle between the incoming laser beam and the normal. The angle of reflection (6.) 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 0; and 6,? The sizes of Qand O become smaller as the angle becomes smaller, and mostly stay in the middle. The line cuts the angle in half. 2. Measure: Set the Angle to 40 degrees and turn on Show protractor. Each marking on the protractor represents 10 degrees. What do 0, and 6, equal? theta_{i} = underline 4 Omega^ * theta*r = 40 deg 50 3. Make a rule: What is the relationship between 0 and 6,? O and O have a equal relationship. They are always the same value. Turn on Show angles and move the Angle slider back and forth. Was your rule correct? Yes, my rule was.correct 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 Angle of incidence (0) 0 Angle of reflection (theta_{r}) 0 0 ^ n 25 deg 25 25 50 deg 50 50 5. Make a rule: How is the mirror angle related to the angles of incidence and reflection? The angles of incidence are always the same as the mirror angle.