How Does Glass Thickness Affect Refractive Index Calculation?

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SUMMARY

The discussion focuses on calculating the refractive index of glass based on the thickness of a photographic plate and the observed halo effect. The specific scenario involves a glass plate that is 3.10 mm thick, resulting in a calculated refractive index of 1.532, which aligns with the textbook answer of 1.53. The participant confirms their understanding of the reflection principles, stating that the angle of incidence equals the angle of reflection, which is crucial for accurate calculations in optics.

PREREQUISITES
  • Understanding of basic optics principles, specifically reflection and refraction.
  • Familiarity with the concept of refractive index and its calculation.
  • Knowledge of geometric optics, including ray diagrams.
  • Experience with light behavior in transparent materials, particularly glass.
NEXT STEPS
  • Study the principles of total internal reflection in optical systems.
  • Learn about the relationship between light wavelength and refractive index.
  • Explore advanced topics in geometric optics, such as Snell's Law.
  • Investigate the effects of different glass thicknesses on optical phenomena.
USEFUL FOR

Students in physics or optics courses, optical engineers, and anyone interested in the practical applications of refractive index calculations in photography and imaging technologies.

kent davidge
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Homework Statement



Old photographic plates were made of glass with a lightsensitive emulsion on the front surface. This emulsion was somewhat transparent. When a bright point source is focused on the front of the plate, the developed photograph will show a halo around the image of the spot. If the glass plate is 3.10 mm thick and the halos have an inner radius of 5.34 mm, what is the index of refraction of the glass? (Hint: Light from the spot on the front surface is scattered in all directions by the emulsion. Some of it is then totally reflected at the back surface of the plate and returns to the front surface.)

Homework Equations



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The Attempt at a Solution


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Is my sketch for the situation correct? I found n = 1.532 and the book answer is also 1.53.
Since the reflected ray is tangent to the upper end of halo, I assumed the ray reflecting half-way in the back surface. Is it correct?

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I think that's right.. the angle of incidence is always equal to the angle of reflection.
 

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