Light Mirrors and Lenses (3379.0K) - McGraw-Hill Higher Education

Using Laser Light Laser light is differentfrom the light produced by the flashlight inseveral ways, as shown in Figure 26. One differenceis that in a beam of laser light, thecrests and troughs of the light waves overlap,so the waves are in phase.Because a laser beam doesn’t spread out asmuch as ordinary light, a large amount ofenergy can be applied to a very small area.This property enables lasers to be used forcutting and welding materials and as areplacement for scalpels in surgery. Lessintense laser light is used for such applicationsas reading and writing to CDs or ingrocery store bar-code readers. Surveyors andbuilders use lasers to measure distances,angles, and heights. Laser beams also are usedto transmit information through space orthrough optical fibers.Figure 26 Laser light is different from the lightproduced by a lightbulb.The light from a bulb contains waves with many differentwavelengths that are out of phase and traveling indifferent directions.The light from a laser contains waves with only onewavelength that are in phase and traveling in thesame direction.SummaryMicroscopes,•Telescopes, and CamerasA compound microscope uses an objectivelens and an eyepiece lens to form an enlarged•image of an object.A refracting telescope contains a large objectivelens to gather light and a smaller eyepiecelens to magnify the image.•A reflecting telescope uses a large concavemirror to gather light and an eyepiece lens to•magnify the image.The image formed by a telescope becomesbrighter and more detailed as the size of the•objective lens or concave mirror increases.A camera uses a convex lens to form an imageon light-sensitive film.•Laser LightLight from a laser contains light waves thatare in phase, have only one wavelength, and•travel in the same direction.Because laser light does not spread out muchas it travels the energy it carries can beapplied over a very small area.Self Check1. Explain why the concave mirror of a reflecting telescopecan be made much larger than the objective lensof a refracting telescope.2. Describe how a beam of laser light is different than thebeam of light produced by a flashlight.3. Explain why the objective lens of a refracting telescopeis much larger than the objective lens of a compoundmicroscope.4. Infer how the image produced by a compound microscopewould be different if the eyepiece lens wereremoved from the microscope.5. Think Critically Explain why the intensity of the lightin a flashlight beam decreases as the flashlight movesfarther away.6. Calculate Image Size The size of an image is relatedto the magnification of an optical instrument by thefollowing formula:Image size magnification object sizeA blood cell has a diameter of 0.001 cm. How large isthe image formed by a microscope with a magnificationof 1,000?ips.msscience.com/self_check_quizSECTION 4 Using Mirrors and Lenses 571