states that for each type of sensory judgment that we make, the measured just noticeable difference (jnd) is a constant proportion of the standard stimulus value used to measure it.

Weber's Law

Explanation:

Ernst Weber, a 19th century psychologist proposed that the size of the difference threshold ( ΔI ) appears to be related to initial stimulus ( I ) magnitude.  

Weber's Law is related to the just noticeable difference or the difference threshold which is the minimum difference in stimulation that a person can detect half of the time.

The formula: ΔI/I = k ( where k signifies the constant proportion)

In order to really perceive a difference, the stimuli must differ by a constant proportion not amount.

  b.

there are isolated pockets of farming, generally around rivers and oases, which are used for irrigation.

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