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

Using Mirrors and LensesMicroscopesFor almost 500 years, lenses have been used to observeobjects that are too small to be seen with the unaided eye. Thefirst microscopes were simple and magnified less than 100times. Today, a compound microscope like the one in Figure 22uses a combination of lenses to magnify objects by as much as2,500 times.Figure 22 also shows how a microscope forms an image. Anobject, such as an insect or a drop of water from a pond, isplaced close to a convex lens called the objective lens. This lensproduces an enlarged image inside the microscope tube. Thelight rays from that image then pass through a second convexlens called the eyepiece lens. This lens further magnifies theimage formed by the objective lens. By using two lenses, a muchlarger image is formed than a single lens can produce.Figure 22 A compound microscopeuses lenses to magnify objects.■ Explain how microscopesmagnify objects.■ Explain how telescopes makedistant objects visible.■ Describe how a camera works.Microscopes and telescopes are usedto view parts of the universe thatcan’t be seen with the unaided eye.Review Vocabularyretina: region on the inner surfaceof the back of the eye thatcontains light-sensitive cellsNew Vocabulary•refracting telescopereflecting telescopeA compound microscopeoften has more than oneobjective lens—eachproviding a differentmagnification. A lightunderneath the objectivelens makes the imagebright enough to seeclearly.Eyepiece lensImage formedby objective lensObjective lensThe objective lensin a compoundmicroscope formsan enlargedimage, which isthen magnified bythe eyepiece lens.Object 567