Unit 3_ Optics_Refraction Lab.pdf - Refraction PhETLab Objectives \u2022 Use ray diagrams to model the refraction of light from air into glass \u2022 Deduce

Unit 3_ Optics_Refraction Lab.pdf - Refraction PhETLab...

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Refraction PhETLab Objectives: Use ray diagrams to model the refraction of light from air into glass. Deduce whether the index of refraction for a material is a constant. Verify Snell’s Law and use it to identify an unknown material. Background: How does light bend? Light travels at different speeds in different media. As light passes at an angle from one medium to another, it changes direction at the boundary between the two media. The index of refraction of a medium, n, is the ratio of the speed of light in a vacuum, c, to its speed in the substance, v. n = c/v When light enters a medium with a higher index of refraction than the medium it is leaving, it bends toward the normal. When light enters a medium with a lower index of refraction than the medium it is leaving, it bends away from the normal. This change of direction of light at the boundary of two media is called refraction. For any light that is traveling from one medium of index of refraction n 1 , at angle of incidence θ 1 , to another medium of index of refraction n 2 , Snell’s law of refraction describes the angle of refraction, θ 2 , experienced by the light. n 1 sin θ 1 = n 2 sin θ 2 For air , the index of refraction is equal to 1, because the speed of light in air is nearly equal to the speed of light in a vacuum. Whenever air is the medium of incidence of the light, Snell’s law can be simplified. n 2 = sin θ 1 / sin θ 2 In this lab, you will measure the angle of refraction of light in a glass slab for a number of different angles of incidence. You then will calculate the index of refraction of the glass. Finally, you will compare the index of refraction for each angle of incidence to verify that it is a constant. Materials: Chromebook or Computer PhET Simulation “Bending Light” at Procedure: Part A Setup 1. Open the simulation “Bending Light” at PhET. Use the address above or use Google. 2. Click on Intro. 3. Leave the default for entry material at “Air”. Choose “Glass” for the exit material (See pic on right). Record the index of refraction of glass into Table 1 4. Choose the protractor and set the laser to an angle of incidence, θ 1 , at 30°. Recall: angles are always measured from the Normal. 5. Ignore the reflected ray (the ray that remains in air). Using the protractor, measure the angle of refraction, θ 2 , of the laser and record in Table 1.
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  • Fall '17
  • Angle of Incidence, Snell's Law, Total internal reflection

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