Lecture_26

# Lecture_26 - 26.6 Lenses A lens is an optical system that...

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26.6 Lenses A lens is an optical system that refracts (bends) light to form an image of the object. A lens consists of two or more surfaces, at least one of which is curved. An optical system with just one lens is called a simple lens system. An optical system more than one lens is called a compound lens system. We know that prisms bend light, so can we use a prism to form an image? Prisms bend the light, but they don’t form clear images. But, if we make the lens with a spherical surface, then incoming parallel rays converge at a common point ( F ), the focal point . Rays don’t intersect at same point. Like for mirrors, we can identify a focal length for the lens ( f ). *Remember, parallel light rays come from objects that are very far away.

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For this lens (bowed outward) the rays converge at a common point: Converging Lens or Convex Lens. If the parallel rays are bent away from the principal axis, they appear to diverge from a common pont: Diverging Lens or Concave Lens . Lenses come in a variety of shapes: Snell’s Law at the interface controls the refraction!
26.7 Formation of Images by Lenses Like mirrors, lenses can form images of objects. But lenses are different, since the light rays actually pass thru the lens. We will again use ray tracing diagrams to determine the location, size, and orientation of images formed by lenses. In doing so, we will assume the lens is thin relative to it’s focal length. This ensures that both d i and d o can be measured from the center of the lens. Also, we will assume, unless otherwise stated, that the object is located on the

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## This note was uploaded on 04/24/2010 for the course PHYS 2002 taught by Professor Blackmon during the Spring '08 term at LSU.

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Lecture_26 - 26.6 Lenses A lens is an optical system that...

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