- THIN LENSES
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- Lenses are found in a huge array of optical instruments, ranging from a simple magnifying glass to a camera’s zoom lens to the eye itself. In this section, we use the Snell’s law to explore the properties of lenses and how they form images.
- HI, My Name is Arnold Sanz from 12-STEM .ZARA
- The word “lens” derives from the Latin word for a lentil bean, the shape of which is similar to a convex lens. However, not all lenses have the same shape. shows a variety of different lens shapes. The vocabulary used to describe lenses is the same as that used for spherical mirrors: The axis of symmetry of a lens is called the optical axis, where this axis intersects the lens surface is called the vertex of the lens, and so forth. Various types of lenses: Note that a converging lens has a thicker “waist,” whereas a diverging lens has a thinner waist.
- A lens is considered to be thin if its thickness t is much less than the radii of curvature of both surfaces, as shown in . In this case, the rays may be considered to bend once at the center of the lens. For the case drawn in the figure, light ray 1 is parallel to the optical axis, so the outgoing ray is bent once at the center of the lens and goes through the focal point. Another important characteristic of thin lenses is that light rays that pass through the center of the lens are undeviated, as shown by light ray 2.In the thin-lens approximation, the thickness d of the lens is much, much less than the radii and of curvature of the surfaces of the lens. Light rays are considered to bend at the center of the lens, such as light ray 1. Light ray 2 passes through the center of the lens and is undeviated in the thin-lens approximation.
- Ray tracing is the technique of determining or following (tracing) the paths taken by light rays.Ray tracing for thin lenses is very similar to the technique we used with spherical mirrors. As for mirrors, ray tracing can accurately describe the operation of a lens. The rules for ray tracing for thin lenses are similar to those of spherical mirrors:
- Ray Tracing and Thin Lenses
- Ray tracing can accurately describe the operation of a lens. Ray tracing for thin lenses is very similar to the technique we used with spherical mirrors. The rules for ray tracing are similar to those of spherical mirrors, except for the size of the lens and the shape of its surface.
- But sir how Ray tracing and thin lense similar to spherical mirrors?
- Work through the following examples to better understand how thin lenses work.Problem-Solving Strategy: LensesStep 1. Determine whether ray tracing, the thin-lens equation, or both would be useful. Even if ray tracing is not used, a careful sketch is always very useful. Write symbols and values on the sketch.Step 2. Identify what needs to be determined in the problem (identify the unknowns).Step 3. Make a list of what is given or can be inferred from the problem (identify the knowns).Step 4. If ray tracing is required, use the ray-tracing rules listed near the beginning of this section.Step 5. Most quantitative problems require the use of the thin-lens equation and/or the lens maker’s equation. Solve these for the unknowns and insert the given quantities or use both together to find two unknowns.Step 7. Check to see if the answer is reasonable. Are the signs correct? Is the sketch or ray tracing consistent with the calculation?

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