Discussion Questions — Part A 65 



DISCUSSION QUESTIONS— PART A 



The following topics are suitable for student reports, term papers, or library 

 examinations in connection with Part A of this text. It is assumed the student 

 will answer the questions with the help of adequate library facilities. 



1. Besides vision and hearing, biophysicists have been active in studies of 

 taste and olfaction. What is the present state of knowledge in these fields? 



2. Insects as well as mammals sense vibrations and sound. Describe the 

 receptor organs, the threshold versus frequency curves, and the equipment 

 necessary to measure vibration and sound thresholds for insects. 



3. Invertebrates respond to light when it falls upon special sensory organs. 

 Describe briefly the simple and compound eyes of insects and the "eye-spot" 

 of Euglena. How is visual acuity possible in the compound eye? 



4. Discuss the evidence concerning any possible role of polarized light in 

 the vision of man, vertebrates, and insects. 



5. At various times, it has been reported that animals could in some way 

 sense or respond to magnetic fields. Review critically the evidence for such 

 a magnetic sense. 



6. Ants communicate and sense direction, in part, by the odor of certain 

 specific chemical compounds which they secrete. These compounds are 

 referred to by various names as pheromones, ectohormones, and chemical 

 releasers. Describe the evidence for such compounds. 



7. Describe in detail the methods for observing the motion of the eardrum 

 (tympanic membrane) and of the ossicles of the middle ear. 



8. Develop the mathematical theory of the Helmholz resonator. How 

 was this type of resonator used to analyze speech ? 



9. Bekesy audiometers are discussed in Chapter 1. Draw up ideal speci- 

 fications for such an audiometer and compare them with those of a com- 

 mercially available model. 



10. The theory of lenses discussed in Chapter 2 uses the infinitesimal 

 approximation of small angles 



sin 6 = 6 



Derive third order equivalent formulas and discuss in terms of these formulas : 

 spherical aberration, coma, field curvature, astigmatism, and image distortion. 

 What is the importance of these various effects for the eye ? 



11. Compare the pulses emitted by several species of bats in terms of sound 

 pressure level, sound frequency, pulse length, and repetition rate. Relate 

 these to the physical structure of the ears, nose, and mouth of the particular 

 species and to their feeding habits. 



12. Describe in considerable detail the experiments indicating that bees 

 can sense the angle of the sun's rays. 



