1. INtroduction to Optical Lenses BY: Maggie Castle

2. Overview Lenses used for visible light wavelengths are usually made from glass They are transparent at the wavelengths your looking for GOAL IN IMAGING: to collect rays and bring them to a common point so you can use a sensor and record the light to make an image each lens has a different dispersion of light and different focal length (see picture examples)

3. Basic Types of Lenses Convex (mag > 1, image is larger)(one side is curved out) Concave (mag <1 image is smaller)(one side is curved in) Bi-Convex (gets larger faster )(two sides are curved out) Bi-Concave (gets smaller faster)(two sides are curved in) Focal Length is next to lens

4. The Ray Model and Finding the Focal Length Rays Model is a simpler model then the Wave model the equation to find focal length is, (1/z 1 ) + (1/z 2 ) = (1/f), where z 1 is the length from the object to the lens, z 2 is the length from the lens to the focal point, and f is the focal length the equation to find the magnification is, M=-(z 2 /z 1 ) You would place a sensor at the focal point to get a focused image Convex have a + focal length (image is on the other side of light) Concave has a - focal length ( image is on the same side as the light source) Since the what you are imaging is on the same side as the image with a concave lens, they are not used in imaging systems. They are used in things such as eye glasses because the image is on the same side as the eye.

5. Advantages and Disadvantages to Lenses Advantage- glass lenses are used in visible light so we are able to see them and the images they create. Lenses are also able to combine with other lenses to increase focus One Problem is that different wavelengths in the visible light spectrum focus at different focal points so it is extremely difficult to get all in focus.

6. Your Turn! These lenses are called tombstone lenses due to the shape If you hold the concave (- focal length) and the larger convex (+ focal length) the image is right side up and smaller If you hold the convex (+ focal length) with the larger convex (+focal length) the image is upside down and larger