Angle of Incidence on a spherical lens

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SUMMARY

The discussion focuses on calculating the angle of incidence on a convex lens, specifically addressing the confusion between normal and tangent lines to the curve. The angle of incidence is measured from the normal, which is defined as the extension of the radius at the point of contact on the lens. The participant seeks clarification on how to determine the angle of incidence at both the entry and exit surfaces of the lens, particularly when given an angle of refraction of 27 degrees. Understanding these concepts is crucial for accurately applying Snell's Law in optical calculations.

PREREQUISITES
  • Understanding of Snell's Law for refraction
  • Basic knowledge of geometry related to circles
  • Familiarity with the concept of normal lines in optics
  • Introduction to derivatives and their application in geometry
NEXT STEPS
  • Study the application of Snell's Law in optical systems
  • Learn how to derive the normal line at any point on a circle
  • Explore the use of derivatives in calculating angles of incidence
  • Investigate the behavior of light in convex lenses and their applications
USEFUL FOR

Students studying optics, physics educators, and anyone involved in optical design or analysis, particularly those working with lenses and refraction principles.

Mitch0
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Firstly, I'm sorry if this is incorrect or if there is a specific place for such questions but as this is neither a problem posed to me, nor something that has been taught - I have little background with which to work with but it is something I need to do for my ERT and 2 maths teachers have been unsuccessful in explaining it.

My dilemma is how to find the incident angle on a convex lens (so any portion of a circle) on the first side, and on the internal surface as it leaves the lens.
I was slightly confused about the normal vs. tangent lines to the curve.

So firstly, is the angle of incidence measured to a normal that is 90* (So, vertically through the lens) or the tangent at that angle of the curve (from the centre of the circle)?
And then how do you find the angle of incidence internally at the second surface interface given the first angle of refraction?
I know how to find the angle of incidence given the angle of the interface, such as on a prism... but how do you find it for a circle, and can it be done with the derivative of the function of a circle? (Or do I also misunderstand the use of derivatives??)

I'm pretty lost on all of this. :/

The only thing my teacher could give me was a triangular prism (which could be drawn inside the circle) where given the angle of refraction was 27 degrees. Then a+b = 180* therefore 27* + b + c2 = 180*.
Where a is the top of the prism, b is the midpoint in line with a, but lower than and between the first interface and the exit interface. Unfortunately I don't know what C refers to as his diagram is so small and he gave no other notes.
 
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The angle of incidence is measured from the normal.

The normal at a point on a circle is the extension of the radius at that point.
 

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