Review 3B - Physics 122 Spring 2009 Document#23 Cycle 3B Review Sheet page 1 of 10 PHYS 122 Cycle 3B Review Sheet Slightly revised to fix inversion

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Physics 122 Spring 2009 – Document #23: Cycle 3B Review Sheet page 1 of 10 PHYS 122: Cycle 3B Review Sheet Slightly revised to fix inversion of refraction rule, May 2, 2009 The Electromagnetic Spectrum: Included here as a reference is a nice graphic representation which describes both frequency and wavelength ranges. You should be able to identify the range of radiation (radio, microwave, IR, visible, UV, X-ray or Gamma ray) based based on the given wavelength. For example if I tell you that I have some electromagnetic waves that are about 1 cm long, you should be able to determine that these are called microwaves. Geometric vs. Physical Optics: The study of Optics divides neatly into two regimes, depending on the size of the wave com- pared to the optical elements of the system: If the wavelength of the light is small compared to the any dimension of the system, we can ignore the details of the wave itself, and treat the light as a simple ray that moves in a straight line from one position to another. We call this regime Geometrical Optics . In this case, we use the technique of ray tracing to follow the path of the light ray as it reflects and refracts through optical components. item If the wavelength of the light is comparable to or larger than any dimension of the system, we cannot ignore the details of the wave. In this case phenomena the light may diffract and/or interfere . This regime is called Physical Optics . To deal with this, we usually apply Huygens’s Principle . Light sources in Geometrical Optics For ray-tracing we assume that any physical object (a person, a pencil, a lightbulb, etc.) is effectively equivalent to a source of light rays, and that these rays are emitted from all positions on that source, and that these rays travel outward in all possible directions. The Cartesian Convention for Ray-Tracing To keep track of what is happening with optical elements (mirrors and lenses), we use a con- vention where the rays of light from a source enter an optical element from left to right. We call the coordinates of the optical element the “zero” position. We define positve and negative as follows: For a Mirror: We define positive as the coordinate on the shiny (refective) side of the mirror (to the left of the mirror). We define negative as the coordiate on the opposite side. For a Lens: We define the position of the object as s as positive if it sits on the “near” side of the lens. We define the coordiate for the image as s as positive if it sits on the “far” side of the lens. The Law of Reflection: Any ideal mirror reflects light according to the rule of reflection: θ = θ
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page 2 of 10 Figure 1: Here is a nice graphic on the Electromagnetic Spectrum that I took from the internet. You should be able to identify the approximate boundaries between each major range.
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This note was uploaded on 11/06/2009 for the course PHYS 122 taught by Professor Raman during the Spring '09 term at Lehigh University .

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Review 3B - Physics 122 Spring 2009 Document#23 Cycle 3B Review Sheet page 1 of 10 PHYS 122 Cycle 3B Review Sheet Slightly revised to fix inversion

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