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Chapter 33. The Nature and Propagation of Light. Reflection and Refraction. Reflection. Reflection. We will focus on specular reflection. The Law of Reflection. All angles are measured with respect to the normal. normal. Multiple reflections. The image. Where is the image?.
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Chapter 33 The Nature and Propagation of Light
Reflection We will focus on specular reflection
The Law of Reflection All angles are measured with respect to the normal. normal
Where is the image? Trace at least two light rays. The image is at where the rays meet. Bring a protractor to class and quizzes and exams.
Where is the image? Trace at least two light rays. The image is at where the rays meet.
Find the refractive index and the speed of light in the liquid
Find θair for the following cases: nwater= 1.33
Solution Total internal reflection
Total internal reflection (TIR) Total internal reflection occurs when θincident > θc. It is when all the refracted light disappear and all the light got reflected back.
The critical angle, θc θc is the angle of incidence θincidencewhen θrefraction = 90o
Wrong Answers! • Define critical angle: • Critical angle is when TIR happens. (Is what???) • Critical angle is the angle of incidence when TIR happens. (TIR happens for many values of θincidence) • Critical angle is the angle when TIR begins. (Which angle???) • Define TIR: • TIR is when the the angle of incidence = critical angle. (What about θincidence>θc?) • TIR is when the the angle of incidence > critical angle. (Circular logic)
Cubic Zirconium Refractive index: 2.15 to 2.18 (diamond: 2.42) Hardness: 8.5 to 9 (diamond: 10) Ingredients: zirconium oxide, magnesium, calcium (diamond: carbon)
Applications of TIR Fiberoptics
Polarizing Filters Electrons on long polymers (long molecules) that moves only in one direction, hence absorbing energy of the E field in that direction, but let the other direction through.
Intensity Rules for Polarizer Make sure you know whether the light is polarized or unpolarized!
Polarization by Reflection At the Brewster angle (or polarizing angle) θp, the reflected beam becomes polarized.
Brewster’s Angle Complete polarization by reflection occurs when the reflected beam is perpendicular to the refracted beam.
Brewster’s Angle Pictures taken with polarizers at different angles. The picture on the right has the reflected light removed by the polarizer to minimize reflection.