Optics 1 - Activities with Light Rays Purpose of this Minilab Apply the basics of ray tracing to learn about reflection and refraction of light

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• Slide 1
• Optics 1 - Activities with Light Rays Purpose of this Minilab Apply the basics of ray tracing to learn about reflection and refraction of light.
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• Optics 1 - Activities with Light Rays Activity 1: Light Reflection at Plane Surfaces nini ntnt Index of refraction of the two materials Angle of incidence Angle of reflection Angle of transmission (refraction)
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• Optics 1 - Activities with Light Rays Law of Reflection: Snells Law of Refraction: Incident, reflected, and transmitted ray lie in one plane. ..the laws..
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• Optics 1 - Activities with Light Rays Checking the law of reflection with a plane mirror 00 45 90 135 180 135 Light Source Polar graph paper ii rr Mirror
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• Optics 1 - Activities with Light Rays Measuring refraction 00 45 90 135 180 135 Light Source Polar graph paper ii tt Semicircular lens Light must hit the center of the flat side Use Snells law to determine n plastic. n plastic
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• Optics 1 - Activities with Light Rays Measuring angle of total internal reflection 00 45 90 135 180 135 Light Source Polar graph paper crit Semicircular lens Light must hit the center of the flat side
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• Optics 1 - Activities with Light Rays Snells Law for Critical Angle =1
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• Optics 1 - Activities with Light Rays Light beam displacement by plane parallel plate Light Source ii tt d t
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• Optics 1 - Activities with Light Rays 00 45 90 135 180 135 Polar graph paper Light beam displacement by plane parallel plate Light Source ii tt d Trace light ray on polar graph paper. Outline location of rectangular plastic on paper. Measure angles i and t. Measure widths d and t. t Let the beam hit the rectangle in center of the polar paper
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• Optics 1 - Activities with Light Rays Light beam displacement by plane parallel plate Use one incident angle i (and corresponding t and d and t) calculate n. Use this calculated n to predict the displacement d for a different incident angle. (Hint: You will also need to use Snells Law for this calculation.) Verify experimentally d for the new angle.
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• Optics 1 - Activities with Light Rays 180 Polar graph paper R 00 45 90 135 Move mirror until curvature matches the curvature on polar graph paper. then measure R as shown. Activity 2: Reflection and Refraction at Spherical Surfaces Getting the Radius of Curvature
• Slide 12
• Optics 1 - Activities with Light Rays Finding the focal point of the concave mirror Regular graph paper: Trace the rays and determine f. Light Source parallel rays f
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• Optics 1 - Activities with Light Rays Finding the focal point of the convex mirror Regular graph paper: Trace the rays and determine f. Light Source parallel rays f Extend the light rays backward to where they seem to come from. Virtual image (isnt really there).
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• Optics 1 - Activities with Light Rays Imaging with the convex mirror Regular graph paper: Trace the rays and determine f. P Light Source Semicircular or Circular lens Here is our object point S
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• Optics 1 - Activities with Light Rays Thin Lens Equation (how to calculate focal length from the radii of a lens and its index of refraction) Each lens has two interface with the air (#1 and #2). Interface #1 is the one that is encountered by the light when entering the lens. Interface #2 is the one that is encountered by the light when exiting the lens. Interface #1 has radius R 1. Interface #2 has radius R 2.
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• Optics 1 - Activities with Light Rays Thin Lens Equation (how to calculate focal length from the radii of a lens and its index of refraction) Sign rules for R 1 : R 1 positive R 1 negative R 2 negative R 2 positive
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• Optics 1 - Activities with Light Rays Example of using the lens equation A double concave lens (concave on interface #1 and also on #2) with both radii being 5cm and the index of refraction n=1.65 : R 1 = - 5 cm and R 2 = + 5 cm
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• Optics 1 - Activities with Light Rays The Imaging Equation for Lenses and Mirrors S: Object Distance P: Image Distance f: Focal Length For Mirrors:where R = Radius of Mirror
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• Optics 1 - Activities with Light Rays Sign Rules For Lenses and Mirrors Convex Lens: + Concave Lens: - Convex Mirror: - Concave Mirror: + f Real objects: S is positive Virtual objects: S is negative Real images: P is positive Virtual images: P is negative Means: a positive number Most objects are real.
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• Optics 1 - Activities with Light Rays Example of signs for f, S, and P P Light Source S Real object Virtual image positivenegative Convex mirror: f is negative
• Slide 21
• Optics 1 - Activities with Light Rays Using the Desk Lamp Dimmer Lamp Plug (black) must be plugged into dimmer plug. Dimmer plug (white) must be plugged into power outlet. On/Off switch of lamp

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