1 / 21

Purpose of this Minilab

Purpose of this Minilab. Apply the basics of ray tracing to learn about reflection and refraction of light. Activity 1: Light Reflection at Plane Surfaces. Angle of incidence. Angle of reflection. Index of refraction of the two materials. n i. n t. Angle of transmission (refraction).

trinh
Download Presentation

Purpose of this Minilab

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Purpose of this Minilab • Apply the basics of ray tracing to learn about reflection and refraction of light.

  2. Activity 1: Light Reflection at Plane Surfaces Angle of incidence Angle of reflection Index of refraction of the two materials ni nt Angle of transmission (refraction)

  3. …..the laws…. Law of Reflection: Snell’s Law of Refraction: Incident, reflected, and transmitted ray lie in one plane. .

  4. Checking the law of reflection with a plane mirror Polar graph paper 45 Qr 0 90 Qi Light Source 45 135 90 180 135 Mirror

  5. Measuring refraction Polar graph paper 45 0 90 Use Snell’s law to determine nplastic. Qi Light Source 45 135 Light must hit the center of the flat side Qt 90 180 135 Semicircular lens nplastic

  6. Measuring angle of total internal reflection Polar graph paper 45 0 90 45 135 Light must hit the center of the flat side Light Source Qcrit 90 180 135 Semicircular lens

  7. Snell’s Law for Critical Angle =1

  8. Light beam displacement by plane parallel plate Light Source Qi Qt t d

  9. Light beam displacement by plane parallel plate Polar graph paper 90 Light Source 135 45 180 Qi 0 Qt Let the beam hit the rectangle in center of the polar paper t 135 45 d • Trace light ray on polar graph paper. • Outline location of rectangular plastic on paper. • Measure angles Qiand Qt. • Measure widths d and t. 90

  10. Light beam displacement by plane parallel plate • Use one incident angle Qi(and corresponding Qtand 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 Snell’s Law for this calculation.) • Verify experimentally d for the new angle.

  11. Activity 2: Reflection and Refraction at Spherical Surfaces – Getting the Radius of Curvature Polar graph paper 90 135 45 Move mirror until curvature matches the curvature on polar graph paper. then measure R as shown. 180 0 R 135 45 90

  12. Finding the focal point of the concave mirror Regular graph paper: Trace the rays and determine f. Light Source parallel rays f

  13. Finding the focal point of the convex mirror Regular graph paper: Trace the rays and determine f. Extend the light rays backward to where they seem to come from. Light Source Virtual image (isn’t really there). parallel rays f

  14. Imaging with the convex mirror Regular graph paper: Trace the rays and determine f. Here is our object point Light Source S P Semicircular or Circular lens

  15. Thin Lens Equation (how to calculate focal length from the radii of a lens and it’s 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 R1. Interface #2 has radius R2.

  16. Thin Lens Equation (how to calculate focal length from the radii of a lens and it’s index of refraction) Sign rules for R1: R1 negative R1 positive R2 positive R2 negative

  17. 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 : • R1 = - 5 cm and R2 = + 5 cm

  18. The Imaging Equation for Lenses and Mirrors S: Object Distance P: Image Distance f: Focal Length For Mirrors: where R = Radius of Mirror

  19. Sign Rules For Lenses and Mirrors f Means: a positive number Convex Lens: + Concave Lens: - Convex Mirror: - Concave Mirror: + Most objects are real. Real objects: S is positive Virtual objects: S is negative Real images: P is positive Virtual images: P is negative

  20. Example of signs for f, S, and P Convex mirror: f is negative Real object Light Source Virtual image S P positive negative

  21. Using the Desk Lamp Lamp Plug (black) must be plugged into dimmer plug. Dimmer plug (white) must be plugged into power outlet. Dimmer On/Off switch of lamp

More Related