The methods of the field of are used to investigate the relationship between the physical properties of a stimulus and observers' perception of the stimulus.

Psychophysics.

Explanation:

As the exercise briefly details, Psychophysics study the relationship between the physical properties of a stimulus and the observers' perception of the stimulus. It's the scientific study of a stimuli and the perception that an individual feels from the reaction to that stimuli. It's a stimulus-response study: psychophysics investigates how much of a stimuli we can detect. For example, when you feel a fabric why is it different from a watermelon? The texture, the smell, even taste. That's what psychophysics study, the perception of the stimuli.

industry had made the u.s. the richest nation in the world at this time. the second industrial revolution caused growth in industry and transportation, which allowed increased trade between nations.

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