. Biophysical science. Biophysics. 2 : 4/ Light and the Eye 45 intensity / can be measured. Therefore, a plot of the fraction of number of correct responses when the light was perceived by the subject against the log / should have the same shape as one of the curves shown in Figure 11. By adding an arbitrary constant to log/, it should be possible to show that the experimental points correspond best to one value of n. This experiment satisfies the criterion of not needing to measure the constant k in Equation 6 and gives unique data for the determination for any individual value of the integer
. Biophysical science. Biophysics. 2 : 4/ Light and the Eye 45 intensity / can be measured. Therefore, a plot of the fraction of number of correct responses when the light was perceived by the subject against the log / should have the same shape as one of the curves shown in Figure 11. By adding an arbitrary constant to log/, it should be possible to show that the experimental points correspond best to one value of n. This experiment satisfies the criterion of not needing to measure the constant k in Equation 6 and gives unique data for the determination for any individual value of the integer n in Equation 8. The value for this constant for some human subjects indicates that n is as high as eight. For other subjects, consistent values as low as one or two have 05. Figure I I. Pn versus log b for quantum threshold calculation. In this graph, Pn is the Poisson distribution probability for n or more events occurring, and b is the average number of events occurring. been found for the number of photons necessary to elicit a visual response. In spite of these individual variations, the human data support the idea that the quantum threshold n is a very low number. Most of these measurements are for rod vision, but there is nothing to indicate that the threshold number of photons absorbed is different for cones. For the human eye, it is impossible to determine whether the response measured is that of a single receptor. It is possible in experiments using invertebrate eyes, such as those of the king crab, limulus. These eyes have only rod-like receptors called ornmatidia. There is one receptor per nerve fiber. For threshold experiments, the eye, with the optic nerve attached, is removed from the animal. The nerve is then dissected until only one nerve fiber remains intact. It then becomes possible to. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations
Size: 1613px × 1550px
Photo credit: © Library Book Collection / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookcollectionbiodiversi, booksubjectbiophysics
