Test Corrections
•Due Tuesday, April 26th
•Corrections must be done in a different inkcolor
•Lots of 4’s for effort – doesn’t mean answer isright!
•Check solutions
•Show formula, explain your conclusions
•Mistake in my solutions
•No points deducted for effort
•One person did it correctly and got 1 point extracredit!
General Physics 2
Geometric Optics
1
General Physics 2
Geometric Optics
2
Geometric Optics
•Ray Model
•assume light travels in straight line
•uses rays to understand and predict reflection &refraction
General Physics 2
Geometric Optics
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Reflection
•Law of reflection
•the angle of incidence equals angle of reflection
•angles are measured from normal
General Physics 2
Geometric Optics
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Reflection
Diffuse reflection
Specular reflection
General Physics 2
Geometric Optics
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Plane Mirrors
General Physics 2
Geometric Optics
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Think-Pair-Share
•How large a mirror do you need to see yourwhole body?
General Physics 2
Geometric Optics
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Spherical Mirrors
By using ray tracing and the law of reflection, you
can figure out where the incoming rays are reflected.
General Physics 2
Geometric Optics
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Focal Point & Focal Length
•Parallel rays striking a concave mirror cometogether at focal point
f = r/2
r = radius of sphere
f = focal length
General Physics 2
Geometric Optics
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Refraction
•index of refraction, n, where c = speed of lightin a vacuum and v = speed of light in thatmedium
•nair = 1
•nglass = 1.5
•Snell’s Law
General Physics 2
Geometric Optics
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Indices of Refraction
General Physics 2
Geometric Optics
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Total Internal Reflection
•Incident angle where refracted angle (2) is 90 is thecritical angle
•at incident angles greater than critical angle, light istotally internally reflected
important forfiber optictechnology(endoscope)
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Geometric Optics
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Thin Lenses
General Physics 2
Geometric Optics
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Focal Length, Focal Plane and Power
•f = focal length
•Power
•inverse of focal length
•P = 1/f
•measured in diopter (D)
•1 D = 1 m-1
General Physics 2
Geometric Optics
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Ray Tracing
General Physics 2
Geometric Optics
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Thin Lens Equation
Thin Lens Equation
Magnification
General Physics 2
Geometric Optics
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Sign Conventions
•focal length
•positive for converging lenses
•negative for diverging lenses
•object distance
•positive if the object is on the side of the lens from which the light iscoming (this is usually the case)
•otherwise, it is negative (virtual object).
•image distance
•positive if the image is on the opposite side of lens from where light iscoming
•positive for real images, negative for virtual images
•image height
•positive if image is upright relative to object, negative for invertedimages
•h0 is always positive
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Geometric Optics
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Combination of Lenses
•When adding two or more lenses in series,the focal length of the combined lenses, f, is:
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Geometric Optics
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Combining Lenses
•Measure the focal length of the two double-convex lensesindividually.
•Combine the lenses together and measure the combinedfocal length.
•Calculate the combined focal length using the equation.
•Calculate the percent error of your measured value.
Activity
•Handouts with practice problems
•Optics Worksheet 1 and 2
General Physics 2
Geometric Optics
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