Thin Lens

1. Melanie Smith Mrs. Grayot, Physics, 6th Wave Project March 18, 2009 Thin Lens

2. Types of Lenses • Lens- a transparent object that refracts light rays such that they converge or diverge to create an image. • Lenses form images by refraction rather then reflection • Lenses are used to form images in optical instruments, such as cameras, telescopes, and microscopes.

3. Types of Lenses cont. • Converging lens- lens that are thicker at the middle • Converging lenses converge light together • Converging lenses are bent inward • Diverging lens- lens that are thicker at the edge • Diverging lenses spread light apart • Diverging lenses are bent outward • Focal Point- definite point • Focal Length is the distance from the focal point to the center of the lens

4. Converging and Diverging

5. Characteristics of Lenses • Real images- formed when rays of light actually intersect to form the image • Virtual images-form at a point from which light rays appear to come but do not actually come • Converging lenses can produce real or virtual images of real objects. • Diverging lenses produce virtual images from real images.

6. Thin-Lens Equation • (1/p)+(1/q)=(1/f) • 1/distance from object lens+1/distance from image to lens=1/focal length • This equation relates object and image distances for a lens.

7. Magnification of Lens • M=(h’/h)=-(q/p) • magnification= image height/object height=-distance from image to lens/distance from object to lens

8. Eyeglasses & Contact Lenses • The transparent front of the eye, called the cornea, acts like a lens, directing light rays toward the light-sensitive retina in the back of the eye.

9. What lenses do for the eye? • Converging lenses help to correct hyperopia or farsightedness. • Hyperopia is when the eye attempts to produce a focused image of a nearby object but the image position is behind the retina. • Diverging lenses help to correct myopia or nearsightedness. • Myopia occurs either when the eye is longer than normal or when the maximum focal length of the lens is insufficient to produce a clear image on the retina.

10. Combinations of Thin Lenses • If two lenses are used to form an image…. • First the image of the first lens is calculated as though the second lens were not present. The light then approaches the second lens as if it had come from the image formed by the first lens. • The image formed by the first lens is treated as the object for the second lens. • Compound microscope use to converging lens.