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Purpose

Purpose. To analyze, through theoretical and experimental methods, the relative luminescence of a series of images produced by multiple reflections in a decorative glass lamp The number of visible images can be used to measure the sensitivity range of the eye. Background.

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Purpose

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Presentation Transcript

  1. Purpose • To analyze, through theoretical and experimental methods, the relative luminescence of a series of images produced by multiple reflections in a decorative glass lamp • The number of visible images can be used to measure the sensitivity range of the eye

  2. Background • Glass oil lamp from Curry Club Restaurant, East Setauket • Inner walls of the glass have a partially reflective coating • Dimensions: 6.5in x 3in x 3in • Glass walls are 0.25in thick and have a brown tint 0.25 in 11 images 6.5 in 3 in

  3. Background (cont.) Top View • When the flame is viewed at eye level, a series of flame images can be seen • Each consecutive image is dimmer than the last and 11-12 images can be seen in a dark room • The nth image is produced by n-1 reflections • The reflectance of the inner wall determines the relative brightness of the image 1st image 2nd image 3rd image 4th image

  4. Procedure - Part 1 I2 I1 I4 • An He-Ne laser and a photo detector were used to measure I1, I2, I3, and I4to calculate the reflectance of the inner and outer surface and the absorption (t) • Incoming light split between absorption, reflection, and transmission Outer Surface I8 I5 Ro = I2 / I1 t = I6 / I5 I7 I6 Inner Surface Ri = I7 / I6 I3

  5. Measured Intensity Values * Ratio of second run to first run. The second run values are lower because the laser power decreased after warm-up but are consistent with the first run.

  6. Analysis and Results • The values of Ri, Ro, and t were derived from a set of equations that contained the measured values of I1, I2, I3, and I4. • t = 1-a and a = absorption ratio • I5 = I1 - I2 • I6 = t*I5 = t*(I1 - I2) • I7 = I6 - I3 = t*(I1- I2)-I3 • I8 = t*I7 = I4 + I8*(I2/I1) • t2*(I1 - I2)-t*I3 - I4/(1 - (I2/I1)) = 0 • Ro = I2/I1 • Ri = I7/I6 = 1 - I3/(t*(I1 - I2)) Results: Ro = 3.2% t = 40.8% Ri = 42.5%

  7. Procedure - Part 2 Laser Iris Photo Detector 5 spots of decreasing intensity • Laser beam allowed to travel through the lamp  5 visible spots • Photo detector used to measure their intensities in Volts using a 100 kΩ resistor & iris used to isolate the images • The ratio of the spot intensities is Ri2 • Ri2 = 19.099% Lamp

  8. Discussion / Conclusion • The reflectance of the inner surface of the glass lamp (Ri) equals the relative luminescence between the flame images • Ri was measured using two independent methods and the 2 values are in very good agreement • Ri = 43.0 ± 0.5% • This value predicts the relative luminescence of the candle flame as shown in the graph below • The nth image is approximately (0.43)n times as bright as the first image • The 11th image is 10, 760 times brighter than the first • Therefore, the human eye can perceive a range of about 10,000 in intensity at a single instant

  9. Future Study • Testing human visual sensitivity • Determining an optimum reflection-transmittance ratio (applications for sunglasses, tinted glass, etc.) • Analyzing or designing “one-way” mirrors • Analyzing laser cavities

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