Elementary biophysics: selected topics elementarybiophy00epst Year: 1963 Threshold intensity /_ Intensity Fig. 17. A schematic representation of the frequency with which a flash of each intensity is seen, for two models. The simple model assumes that each flash has the same number of photons. The fluctuation model takes into account the fact that a given average number of photons (plotted on the abscissa) will have a fluctuating number of photons in each individual flash, for experimental reasons. Intensity of the light flashes (on a logarithmic scale) Fig. IS. Calculated curves of the fr
Elementary biophysics: selected topics elementarybiophy00epst Year: 1963 Threshold intensity /_ Intensity Fig. 17. A schematic representation of the frequency with which a flash of each intensity is seen, for two models. The simple model assumes that each flash has the same number of photons. The fluctuation model takes into account the fact that a given average number of photons (plotted on the abscissa) will have a fluctuating number of photons in each individual flash, for experimental reasons. Intensity of the light flashes (on a logarithmic scale) Fig. IS. Calculated curves of the fraction of times a light flash will contain at least n photons for the average intensity plotted on the abscissa. a fluctuating number of photons, and only flashes containing at least the threshold number will be seen. As the intensity increases, a steadily in- creasing proportion of flashes will exceed the threshold number. Finally, intensities will be reached for which, despite the fluctuations, all flashes will exceed the threshold number of photons. The simple model and the fluctuation model are presented schemati- cally in Fig. 17. A flash of a given intensity is presented repeatedly to the subject, and the fraction of times he sees the flash is recorded. Then, in succeeding experiments, using a series of intensities, similar data are recorded. The data are then plotted to show the fraction of times the flash is seen for each incident intensity.
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