The focal length of the convex lens-محول.pdf

The focal length of the convex lens Group B3 / BY: MOHAMED AHMED JASIM Medica l phy sics / 13th Feb pg. 1 TABLE OF CONTENTS Introduction ..………....….….…………….….…….3 Method ..………..…..…..….….…….............…….4 Discussion …………..……..….….……..…….…….5 Results ..………..…....……..….….…..……….…….6 BY: MOHA...

The focal length of the convex lens Group B3 / BY: MOHAMED AHMED JASIM Medica l phy sics / 13th Feb pg. 1 TABLE OF CONTENTS Introduction ..………....….….…………….….…….3 Method ..………..…..…..….….…….............…….4 Discussion …………..……..….….……..…….…….5 Results ..………..…....……..….….…..……….…….6 BY: MOHAMED AHMED JASIM pg. 2 INTRODUCTION Before the 1590s, simple lenses dating back as far as the Romans and Vikings allowed limited magnification and simple eyeglasses. Zacharias Jansen and his father combined lenses from simple magnifying glasses to build microscopes and, from there, microscopes and telescopes changed the world. Understanding the focal length of lenses was crucial to combining their powers. Types of Lenses There are two basic types of lenses: convex and concave. Convex lenses are thicker in the middle than on the edges and cause light rays to converge to a point. Concave lenses are thicker on the edges than in the middle and cause light rays to diverge. Convex and concave lenses come in different configurations. Plano-convex lenses are flat on one side and convex on the other while bi-convex (also called double-convex) lenses are convex on both sides. Plano-concave lenses are flat on one side and concave on the other side while bi-concave (or double-concave) lenses are concave on both sides. A combined concave and convex lens called concavo-convex lenses is more commonly called the positive (converging) meniscus lens. This lens is convex on one side with a concave surface on the other side, and the radius on the concave side is greater than the radius of the convex side. A combined convex and concave lens called a convexo-concave lens is more commonly called a negative (divergent) meniscus lens. This lens, like the concavo-convex lens, has a concave side and a convex side, but the radius on the concave surface is less than the radius on the convex side. Focal Length Physics The focal length of a lens f is the distance from a lens to the focal point F. Light rays (of a single frequency) traveling parallel to the optical axis of a convex or a concavo-convex lens will meet at the focal point. A convex lens converges parallel rays to a focal point with a positive focal length. Because the light goes through the lens, positive image distances (and real images) are on the opposite side of the lens from the object. The image will be inverted (up-side down) relative to the actual image. A concave lens diverges parallel rays away from a focal point, has a negative focal length and forms only virtual, smaller images. Negative image distances form virtual images on the same side of the lens as the object. The image will be oriented the same direction (right-side up) as the original image, just smaller Subheading Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Purus in massa tempor nec feugiat nisl pretium. Aliquam vestibulum morbi blandit cursus risus at ultrices mi. Ut morbi tincidunt augue interdum velit euismod in. Tortor posuere ac ut consequat semper viverra nam libero. Egestas sed sed risus pretium quam vulputate. Nunc mattis enim ut tellus elementum sagittis vitae et. Tristique senectus et netus et. Pulvinar neque laoreet suspendisse interdum consectetur libero id faucibus. Lacus laoreet non curabitur gravida arcu ac. Odio facilisis mauris sit amet. BY: MOHAMED AHMED JASIM pg. 3 METHOD Purpose: To determine te focal length of the converging lens by using: 1. A plane mirror. 2. A graphical method. Apparatus: 1. Converging lens. 2. Holder. 3. Plane mirror. 4. Meter scale. 5. Mounted pin (object). 6. Screen. Procedure: Part 1 1. Obtain a rough value F´for the focal length of the lens by focusing the image of the window on a screen. 2. Measure the distance between the lens and the image (F´) 3. Repeat two times at different places along the optical bench or scale and take the mean of the results. F´= rough value for the focal length of the lens. window (object) screen (image) F´ Part 2 1. place an object pin at a distance from the lens equal to 2 F ́. Measure the distance between the object and lens , which is called (U). 2. Locate the position of is real image on the other side of the lens, by using a screen. Measure the distance between the image and lens, Which is called (V). 3. Move the object to other position both nearer to and farther away from the lens, locating the new position of the image each time. BY: MOHAMED AHMED JASIM pg. 4 DISCUSSION Theory and calculation: 1/F = 1/U +1/V A straight line inclined at 45o each axis is obtained. The intercept on the 1/V axis is the numerical value for which 1/U =0. 1/F1 =1/U +1/V = 0 + 1/V F1 = V ................. (1) Similarity for the intercept on the 1/V axis . F2=U Take the mean value of the two intercepts. F1 +F2 F = (......) cm BY: MOHAMED AHMED JASIM pg. 5 RESULTS u v 1/u 1/v 8 42 0.125 0.02 11 51 0.09 0.019 14 58 0.07 0.017 17 61 0.098 0.016 20 65 0.05 0.015 1. Plot a graph of 1/U against 1/V. 2. Draw the straight line through the pointed and produce it to intersect both axes. Conclusion: BY: MOHAMED AHMED JASIM pg. 6