Chapter 15 Exercises
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FIGURE 15.21 Light confined to travel inside a glass cylinder by total reflection.
The two bundles as a unit are introduced into the body through orifices, veins, or arteries and are threaded toward the organ to be examined. Light
from a high intensity source, such as a xenon arc lamp, is focused into onebundle which carries the light to the organ to be examined. Each of the fibersin the other bundle collects light reflected from a small region of the organand carries it back to the observer. Here the light is focused into an imagewhich can be viewed by eye or displayed on a cathode ray or some othertype of electronic screen. In the usual arrangement, the illuminating bundlesurrounds the light-collecting bundle. Most endoscopes now utilize attachedminiature video cameras to form images of the internal organs for display onTV monitors.
The use of fiber-optic devices has been greatly expanded by attaching to the endoscope remotely controlled miniature instruments to perform surgical operations without major surgical incisions. More recent applicationsof fiber optics include measurement of pressure in arteries, bladder, anduterus using optical sensors and laser surgery where powerful laser light isdirected through one of the bundles to the tissue which is selectively destroyed(see Chapter 16).
EXERCISES
15-1. Compute the change in the position of the image formed by a lens with a focal length of 1.5 cm as the light source is moved from its position at6 m from the lens to infinity.
15-2. A point source of light that is not exactly in focus produces a disk image at the retina. Assume that the image is acceptable provided the imagediameter of the defocused point source is less than a. Show that thedepth of field is inversely proportional to the diameter of the aperture.
Chapter 15 Optics 15-3. Using data presented in the text, calculate the focusing power of the cornea and of the crystalline lens.
15-4. Calculate the refractive power of the cornea when it is in contact with water. The index of refraction for water is 1.33.
15-5. Calculate the focusing power of the lens in the fish eye. Assume that the lens is spherical with a diameter of 2 mm. (The indices of refractionare as in Table 15.1.) The index of refraction for water is 1.33.
15-6. Calculate the distance of the point in front of the cornea at which paral lel light originating inside the reduced eye is focused.
15-7. Using the dimensions of the reduced eye (Fig. 15.5), calculate the angu lar resolution of the eye (use Fig. 15.6 as an aid) (a) with a single unexcited cone between points of excitation (b) with four unexcited conesbetween areas of excitation.
15-8. Calculate the distance from which a person with good vision can see the whites of another person’s eyes. Use data in the text and assume thesize of the eye is 1 cm.
15-9. Calculate the size of the retinal image of a 10-cm leaf from a distance of 500 m.
Atomic Physics
Modern atomic and nuclear physics is among the most impressive scientificachievements of this century. There is hardly an area of science or technology that does not draw on the concepts and techniques developed in this field.
Both the theories and techniques of atomic and nuclear physics have playedan important role in the life sciences. The theories provided a solid foundation for understanding the structure and interaction of organic molecules, andthe techniques provided many tools for both experimental and clinical work.
Contributions from this field have been so numerous and influential that it isimpossible to do them justice in a single chapter. Of necessity, therefore, ourdiscussion will be restricted to a survey of the subject. We will present a briefdescription of the atom and the nucleus, which will lead into a discussion ofthe applications of atomic and nuclear physics to the life sciences.
16.1
The Atom
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