Concept explainers
Predict/Calculate With unaided vision, a librarian can focus only on objects that lie at distances between 5.0 m and 0.50 m. (a) Which type of lens (converging or diverging) is needed to correct his nearsightedness'? Explain. (b) Which type of lens will correct his farsightedness? Explain. (c) Find the refractive power needed for each part of the bifocal eyeglass lenses that will give the librarian normal visual acuity from 25 cm out to infinity (Assume the lenses rest 2 0 cm from his eyes.)
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- A cataract-impaired lens in an eye may be surgically removed and replaced by a manufactured lens. The focal length required for the new lens is determined by the lens-lo-retina distance, which is measured by a sonar-like device, and by the requirement that the implant provide for correct distance vision. (a) If the distance from lens to retina is 22.4 mm, calculate the power of the implanted lens in diopters. (b) Since there is no accommodation and the implant allows for correct distance vision, a corrective lens for close work or reading must be used. Assume a reading distance of 33.0 cm, and calculate the power of the lens in the reading glasses.arrow_forwardConstruct Your Own Problem Consider a telescope of the type used by Galileo, having a convex objective and a concave eyepiece as illustrated in part (a) of Figure 2.40. Construct a problem in which you calculate the location and size of the image produced. Among the things to be considered are the focal lengths of the lenses and their relative placements as well as the size and location of the object. Verify that the angular magnification is greater than one. That is, the angle subtended at the eye by the image is greater than the angle subtended by the object.arrow_forwardChoose the option from each pair that makes the following statement correct. For a farsighted person, the [(a) near point; (b) far point] is always located farther than 1 (c) 1 m; (d) 25 cm] from the eye and lens corrective lens is [(e) converging; (f) diverging).arrow_forward
- How far from the lens must the film in a camera be, if the lens has a 35.0-mm focal length and is being used to photograph a flower 75.0 cm away? Explicitly show how you follow the steps in the Problem-solving strategy: Lenses.arrow_forwardChoose the option from each pair that makes the following statement correct. For a nearsighted person, the [(a) near point; (b) far point] is always located closer than [(c) infinity; (d) 25 cm] from the eye and the corrective lens is [(e) converging; (f) diverging].arrow_forwardTo fit a contact lens to a patient's eye, a keratometer can be used to measure the curvature of the corneathe front surface of the eye. This instrument places an illuminated object of known .size at a known distance p from the cornea, which then reflects some light from the object, forming an image of it The magnification M of the image is measured by using a small viewing telescope that allows a comparison of the image formed by the cornea with a second calibrated image projected into the field of view by a prism arrangement. Determine the radius of curvature of the cornea when p = 30.0 cm and M = 0.013 0.arrow_forward
- A person with a nearsighted eye has near and far points of 16 cm and 25 cm, respectively. (a) Assuming a lens is placed 2.0 cm from the eye, what power must the lens have to correct this condition? (b) Suppose contact lenses placed directly on the cornea are used to correct the person's eyesight. What is the power of the lens required in this case, and what is the new near point? Hint: The contact lens and the eyeglass lens require slightly different powers because they are at different distances from the eye.arrow_forwardConstruct Your Own Problem Consider a telescope of the type used by Galileo, having a convex objective and a concave eyepiece as Illustrated in Figure 26.23(a). Construct a problem in which you calculate the location and size of the image produced. Among the things to be considered are the focal lengths of the lenses and their relative placements as well as the size and location of the object. Verity that the angular magnification is greater than one. That is, the angle subtended at the eye by the image is greater than the angle subtended by the object.arrow_forwardIt has become common to replace the cataractclouded lens of the eye with an internal lens. This intraocular lens can be chosen so that the person has perfect distant vision. Will the person be able to read without glasses? If the person was nearsighted, is the power of the intraocular lens greater or less than the removed lens?arrow_forward
- Unreasonable Results A boy has a near point of 50 cm and a far point of 500 cm. Will a 4.00 D lens correct his far point to infinity?arrow_forwardUnreasonable Results Your friends show you an image through a microscope. They tell you that the microscope has an objective with a 0.500-cm focal length and an eyepiece with a 5.00-cm focal length. The resulting overall magnification is 250,000. Are these viable values for a microscope? Unless otherwise stated, the lens-to-retina distance is 2.00 cm.arrow_forwardDuring LASIK eye surgery (laser-assisted in situ keratomileusis), the shape of the cornea is modified by vaporizing some of its material. If the surgery is performed to correct for nearsightedness, how does the cornea need to be reshaped?arrow_forward
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