The examination is in four parts, each worth 25%. There will be a moderate but significant grade reduction if exams are not in by Friday, March 19, 1965, 3:00 p.m.
1. Von Bekesy recently (1961) received the Nobel Prize for his outstandingly fine work related to the processes of audition.
a) With a set of references to your sources of information beyond the regular textbook, make a brief resumé of his contribution setting it into the general modern picture of auditory transduction from sound wave striking the external ear of a higher vertebrate into nerve impulse patterns.
b) If, as was demonstrated in class, the direction from which B click sound arrives can be discriminated to within about 100 in the horizontal plane by even an unpracticed observer, calculate, using appropriate constants, the time differences that could be assigned to click signal components arriving at the two ears and reconcile these numbers with the well established refractory period and maximal frequency response of even fast responding nerves.
c) If a bat, closing in at a speed of 15 m.p.h. on a relatively slow moving insect, emits its sound ranging cry at 30,000 c.p.s., what frequency or frequencies will it hear in the echo?
2. a) Give a reasonable biophysical explanation for the existence of “non spectral” colors such as brown and purple which have great subjective reality and distinctiveness but which are never found in a spectrum dispersed from a light source wherein every frequency in the light is displayed somewhere.
b) In connection with the above problem, explain semi-mathematically why it is interesting to view a brown object in dim, intermediate and bright light to see whether its apparent color changes. Is there a nearly equivalent acoustic experiment?
3. Ordinary “wash machine” class motors produce continuously about 1/50 of a horsepower per pound of their weight while “sprint” motors such as those used to actuate airplane flaps or propeller pitch may produce roughly ten times as much ‘specific” power for short periods. Using data from reasonably reliable sources, i.e. not a mere guess, work out corresponding ratings for human muscle. Show bow you get to your results as there are many alternate approaches that are acceptable and the reasoning is at least as important as the quantitative result.
4. Given a perfect “nerve clamp” experimental set-up in which you could impose any desired pattern of potential with time across the active axon membrane and could measure the accompanying current pattern, describe and sketch (draw accurately if you can) one pattern of changing potential for which you can confidently predict the resulting current pattern with time and describe a second experiment that would answer an important question about the nerve excitation process.