Section 3 review
A single optical element might be useful for a bathroom mirror or magnifying glass, but most technologies that use optics include more than one optical device and are called compound optics. The refracting telescope and microscope are historically important optical instruments that produce inverted and magnified images. In their basic design, both use two lenses; the image formed by the first lens acts as the object for the second lens. Modern binoculars use multiple lenses, but they also take advantage of internal reflections within a pair of prisms so that the image is upright. The human eye uses a lens with variable shape (or focal length) to focus on objects either nearby or far away. Within the human eye, rods and cones detect the intensity and colors of light, respectively. Read the text aloud
rods, cones

Review problems and questions

  1. Do the lenses in a camera produce a real or a virtual image? Read the text aloud Show
  1. Why is your vision sharpest when the pupils of your eyes are contracted or very narrow? Read the text aloud Show
  1. Identify the part of the human eye that causes each of the following vision problems and what is used to correct for it.
    1. farsightedness
    2. nearsightedness
    3. color blindness
    4. astigmatism Read the text aloud Show
  1. Imagine using the optical telescope you constructed in Investigation 21D on page 1233 to create an image on a screen of the letter “F” printed on a piece of paper. Now cover up the top half of the entrance (or objective) lens for the telescope.
    1. Will you continue to see the entire letter “F” or only part of it?
    2. Will the image magnification be changed?
    3. Will the brightness of the image change?
    4. Explain your answers for parts a through c. Read the text aloud Show
  1. A microscope usually has a rotating set of objective lenses of different focal lengths. A student was using the objective lens with a 10 mm focal length and found that the images were magnified 40 times. What will happen to the magnification if the student switches to an objective lens with a shorter, 4 mm focal length? Read the text aloud Show

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