# 2 - Seeing Objects Before studying the images formed by...

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1 Geometrical Optics 2 Image Formation by Reflection: Mirrors Seeing Objects Before studying the images formed by mirrors, rfaces lenses we must first understand this: surfaces, lenses, we must first understand this: how do we see an object? In order for the eye to see an object, rays of light from that object must enter the eye Seeing Objects, cont’d Light leaves the object in all directions When determining what an observer sees, we follow light rays from the object to the observer’s eye Paraxial Approximation Light passes through mirrors, surfaces and lenses ccording to the laws of reflection and refraction according to the laws of reflection and refraction, producing images Consider ideal models via paraxial approximation in which rays only make small angles with optical xis axis Actual optical systems exhibit aberrations (e.g. blurring, astigmatism, coma, etc.)

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2 Example of an Aberration: figure shows many rays striking the spherical mirror some rays coming in at large angles to the axis these rays do not all come to the me image point same image point we shall not consider such rays example of Spherical Aberration Finding Images Light originates from the object O , normally Eye intercepts rays from the image I , as if O were at the image point Draw a Ray Diagram!!! To find where an image is formed, it is always necessary to follow at least two rays of light from O as they reflect from the mirror (a 3 rd is a good check) Mirrors Notation for Mirrors and Lenses The object distance s : distance from the object O to the mirror or lens The image distance s’ : distance from the image I to the mirror or lens Images are formed at the point where rays actually intersect or appear to originate The (lateral) magnification m of the mirror or lens is the ratio of the image height to the object height an inverted image has a negative magnification !!
3 Flat Mirror: Ray Diagram, with Labels and Characterization of Image ss Mirror •rays start at H •one follows path HM and reflects back on itself •second ray follows path HV and reflects according to the Law of Reflection Types of Images for Mirrors and Lenses A real image is one in which light actually passes through the image point I Real images can be displayed on screens, or recorded on film A virtual image

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2 - Seeing Objects Before studying the images formed by...

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