The Optics of Mirrors

Transcription

1 Use with Text Pages The Optics of Mirrors Use the terms in the list below to fill in the blanks in the paragraphs about mirrors. reversed smooth eyes concave focal smaller reflect behind ray convex optical upside down virtual plane length real spread upright Mirrors can be formed by almost any smooth surface. Flat mirrors made from glass with a reflective coating on the back surface are called plane mirrors. To see your face in a mirror, light has to reflect off your face. This light goes to the mirror and is reflected toward your eyes. The image you see will be reversed from left to right. To explain this requires the use of a ray model. The image will appear to come from behind the mirror. Since there is nothing behind the mirror, this image is called a virtual image. Mirrors that have a curve like the bowl of a spoon are called concave mirrors. A straight line going through the center of a mirror is called the optical axis. Beams of light parallel to this axis will strike a concave mirror and be reflected to pass through a point on the optical axis called the focal point. The distance from the center of the mirror to the focal point is called the focal length. When a concave mirror is used to reflect light from an object that is placed farther from the mirror than the focal point, the image formed will be a real image. The image will be enlarged and upside down. If the object is placed between the focal point and the mirror, an image is seen that is enlarged in size, upright, and seems to be behind the mirror. Because the image appears to be behind the mirror, it cannot be projected onto a screen like a real image and is therefore called a virtual image. A type of mirror like the back of a spoon is called a convex mirror. The rays that are reflected from this mirror are always spread out. When this happens, the image will appear to be behind the mirror and be upright but smaller than the original object. 82

2 Use with Text Pages The Optics of Lenses Use the terms in the list below to fill in the blanks in the paragraphs about lenses. concave longer larger curved convex length clearly object thick shape lens retina less refracting inverted muscles virtual cornea astigmatism Lenses are made of transparent material and have a surface. A convex lens has thin edges and a middle. Another type of lens is thicker at the edge than the middle and is called a lens. All lenses work by light. Parallel rays of light are refracted toward each other and brought to a focal point in a lens. Light is refracted both when it enters and leaves a. The amount of refraction depends on the change of the speed of light as it passes through a material and on the of the lens. In a convex lens, the type of image formed depends on the position of the and the focal length of the lens. When the object is more than twice the focal length from the lens, the real image is smaller than the object and. If the object is between one and two focal lengths, the image is than the object and inverted. When the object is between the lens and the focal point, the image is larger and upright but is a image. Concave lenses are not able to produce real images and are used with convex lenses to create a focal length. The light we see enters our eyes through the transparent covering of the eye called the. The light then passes through the pupil and converges on the back part of the eye called the. Images are properly focused on the retina by the convex lens in the eye, which is controlled by eye. To focus images of distant objects, a longer focal is needed. To do this, the muscles relax, allowing the lens to be convex. People are farsighted when they can see things far away but have fuzzy vision at close range. To correct this problem, a lens is used. A lens is used to correct the vision of a nearsighted person. An eye problem caused by an unevenly curved cornea is. 83

3 Use with Text Pages Optical Instruments Match the definitions in Column II with the terms in Column I. Write the letter of the correct definition in the blanks beside Column I. Column I Column II d 1. optical instruments h 2. aperture f 3. telescope c 4. wide-angle and telephoto lenses a 5. refracting telescope j 6. reflecting telescope b 7. objective i 8. microscope e 9. binoculars g 10. camera a. uses two convex lenses to gather and focus light from distant objects b. convex lens with a long focal length located where light enters an optical instrument c. special lenses that enable photographers to take pictures with different effects d. devices that are designed to aid the human eye in making observations e. operate on same principle as a refracting telescope and has a lens for each eye f. devices designed to magnify objects that are very far away g. gathers light through a lens and projects an image on light-sensitive film h. an opening where light enters a camera i. uses two convex lenses with relatively short focal lengths to magnify very small, close objects j. uses a concave mirror, a plane mirror, and a convex lens to magnify distant objects Find the following terms in the hidden word puzzle: binoculars, camera, microscope, reflecting, refracting, and telescope. The terms can be written horizontally or vertically. A B E R E F R A C T I N G M I C R O S C O P E A L D I N M F J C O S B L E Q H N O R R U A L M V E I U V P C B E T N D P B S Q T I Z U A F Y F L E I C U H A B L K L P E S Z F O G C H C A M E R A Z Y R P R J E O R N C X G M D A E W V L Y S O T N K J B H F X K V X C G I W K N I O G J U D F S Z N M R D P C H T P K B J O G Q S M L Q T W G C 84

4 Use with Text Pages The Hubble Space Telescope Determine whether the italicized term makes each statement true or false. If the statement is true, write the word true in the blank. If the statement is false, write in the blank the term that makes the statement true. 1. The Hubble Space Telescope is named after Edwin P. Hubble, an astronomer. 2. Our view of outer space from the surface of Earth is blurred by Earth s oceans. 3. The Hubble Space Telescope is designed to detect infrared and visible light in space that usually cannot be detected by telescopes at Earth s surface. 4. Electrical power is supplied to the telescope s system by the electric company. 5. NASA is the abbreviation for the National Airways and Space Administration. 6. The Hubble Space Telescope is in an orbit about 100 kilometers above Earth. 7. The final cost of the Hubble Space Telescope is about 2 million dollars. 8. The Hubble Space Telescope was launched by NASA on April 20, The Hubble Space Telescope produces images that are five times sharper than powerful telescopes on Earth. 10. The universe appears to be contracting. Answer the following question on the lines below. Use complete sentences. 11. What do scientists hope to learn by using the Hubble Space Telescope? What would you like to study in outer space? Why? 85

5 Use with Text Pages Solve the following crossword puzzle by using the clues provided. Applications of Light Across 2. With this type of light, transverse waves vibrate only on one plane. (2 words) 4. Lasers are used to read these in grocery stores. (2 words) 6. Almost parallel light rays that do spread out are an example of this type of light. 7. photons travel in the same phase and directions as the original photon. Down 1. These are transparent glass fibers that can pipe light from one place to another. (2 words) 3. This is a device that reduces a light source to the size of a single atom. 5. These use polarizing filters to block out glare. (2 words) 8. Polarizing sunglasses block this out. 9. Optical fibers are most commonly used in this. 86