Lectures on imagne formation

Lectures on imagne formation - Image formation When light...

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Image formation • When light rays encounter objects, these rays change their direction due to reflection and refraction • When these reflected and refracted rays are detected by an observer, objects that radiated these rays appear to be displaced from their true locations • We will study how images Notes are formed by mirrors (reflection) and lenses (refraction). Geometric (ray) optics is enough for understanding of images
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Image formation by Mirrors and Lenses The object distance is the distance from the object to the mirror or lens – Denoted by p The image distance is the distance from the image to the mirror or lens – Denoted by q The lateral magnification of the mirror or lens is the ratio of the image height to the object height – Denoted by M Notes Image Object Lens q p
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Images Formed by Flat Mirrors • Simplest possible mirror • Light rays leave the source O and are reflected from the mirror • Point I is called the image of the object at point O Notes Images are always located by extending diverging rays back to a point at which they intersect
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Types of Images • There are two types of images: real and virtual • The image seen in a mirror is virtual image • A real image is formed when light rays pass through and diverge from the image point Notes • A virtual image is formed when light rays do not pass through the image point but only appear to diverge from that point
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Images Formed by Flat Mirrors, 2 • A flat mirror always produces a virtual image • Geometry can be used to determine the properties of the image • There are an infinite number of hoices of direction in which light Notes choices of direction in which light rays could leave each point on the object • Two rays are needed to determine where an image is formed
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Images Formed by Flat Mirrors, 3 • Consider a mirror image of an arrow • One ray starts at point P , travels to Q and reflects back on itself • Another ray follows the path Notes PR and reflects according to the law of reflection • The triangles PQR and P’QR are congruent
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Images Formed by Flat Mirrors, 4 • To observe the image, the observer would trace back the two reflected rays to P’ • Point P’ is the point where the rays appear to have originated he image formed by an object Notes The image formed by an object placed in front of a flat mirror is as far behind the mirror as the object is in front of the mirror | p | = | q |
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Lateral Magnification • Lateral magnification, M , is defined as – This is the general magnification for any pe of mirror Image height Object height ' h M h = Notes type of mirror – It is also valid for images formed by lenses – Magnification does not always mean bigger, the size can either increase or decrease M can be less than or greater than 1 The lateral magnification of a flat mirror is 1
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Spherical Mirrors • A spherical mirror has the shape of a section of a sphere • The mirror focuses incoming parallel rays to a point (only
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Lectures on imagne formation - Image formation When light...

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