Psychophysics is the study of the relationship between physical stimuli and the behavior or mental experiences the stimuli evoke. Gustav Fechner was the most significant figure in history of psychophysics. He provided a set of procedures to relate the intensity of a physical stimulus (measured in physical units) to the magnitude of the sensory experience ( measured in psychological units). It has been determined that there are different thresholds. Absolute threshold is the smallest detectable level of stimulus. I can speak personally on this topic because I have taken many hearing tests, which is absolute threshold test. An issue that occurs is that at these low levels of pitches and tones sometimes you hear them and sometimes you think you hear them. Because of this absolute threshold is the lowest intensity at which a stimulus can be detected 50% of the time. The difference threshold is defined as the point at which the stimuli are recognized as different half the time(Psychology and Life). This threshold is known as just noticeable difference. Weber's Law is related to the Just Noticeable Difference which is the minimum difference in stimulation that a person can detect 50 percent of the time. But Ernst Weber noted that for people to really perceive a difference, the stimuli must differ by a constant "proportion" not a constant "amount. (http://www.alleydog.com). For example, when buying a laptop that costs $1,000 you want to add more memory which costs $200. In this case $200 is out of your range and seems to high. But if you were to buy a house that costs $300,000 adding a $200 upgrade feature seems like nothing. It would take a couple thousand to make you reconsider. In this example, the amount stays the same, but the proportion changes and that's what makes the perceptual difference.
Summarize the workings of either the visual or hearing system.
To understand the visual