Optics Lenses Analogy Mirrors make images with reflection

Optics: Lenses

Analogy… • Mirrors make images with reflection • Lenses make images with refraction! 2

Remember…. • Virtual images are located where reflected light appears to converge • Real images are located where reflected light actually converges 3

Convex Lenses Thicker in the center than edges. Two focii (one on either side) Lens that converges (brings together) light rays. – Light traveling is refracted through lens, then refracted again back into air – Any ray traveling parallel Will be refracted through focal point

Convex Lenses – Lens that converges (brings together) light rays. – Forms real images and virtual images depending on position of the object The Magnifier

Lens Ray Diagram Rules • Three Rays: 1. Ray goes parallel, refracted through f (on other side) 2. Ray goes through f (on same side), gets refracted parallel (on other side) 3. Ray goes through the center of lens 6

Concave Lenses • Lenses that are thicker at the edges and thinner in the center. – Diverges light rays – All images are right side up and reduced. The De-Magnifier

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How You See • Near Sighted – Eyeball is too long and image focuses in front of the retina – • Near Sightedness Concave lenses expand focal length • Far Sighted – Eyeball is too short so image is focused behind the retina. • Far Sightedness – Convex lens shortens the focal length.

Cameras, in brief object pinhole image at film plane In a pinhole camera, the hole is so small that light hitting any particular point on the film plane must have come from a particular direction outside the camera object image at film plane lens In a camera with a lens, the same applies: that a point on the film plane more-or-less corresponds to a direction outside the camera. Lenses have the important advantage of collecting more light than the pinhole admits