Lenses

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Lenses


Lecture number:
25
Pages:
4
Type:
Lecture Note
School:
The University of Vermont
Course:
Phys 012 - Elementary Physics
Edition:
1
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Lecture 25 Outline of Last Lecture I. Total Internal Reflection a. As θ1 increases, θ2 also increases. b. At the critical angle, refracted light will follow the surface between the two media (θrefracted = 90 degrees). c. Any angle of incidence greater than the critical angle will result in total internal reflection (all light reflected, none entering second medium). i. Only happens when light beam goes from higher index of refraction to lower index of refraction (n1 > n2). ii. θc = sin-1(n2/n1) d. Problem: A beam of light is incident on the circular face of a glass cylinder at an angle of θ1. Find the maximum value of θ1 to get total internal reflection in the glass cylinder. i. θ1 will be at max value for T.I.R. when θ3 is at critical angle. ii. ngsinθ3 = nasin(90) = na iii. θc = θ3 = sin-1(na/ng) = 47.3 degrees iv. θ2 = 90 – θ3 = 42.6 degrees v. nasinθ1 = ngsinθ1 vi. θ1 = sin-1([ngsinθ2]/na) = 67.1 degrees III. Brewster’s Angle: angle at which light becomes completely polarized parallel to the reflecting surface (electric field will oscillate parallel to reflecting surface). Physics 012 1st Edition



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