Q.Explain the functional limitations of sense organs.

Our sense organs do not respond to every possible stimulus -- each one works only within a limited range of intensity, and psychologists measure these limits using the concepts of absolute and difference thresholds.

Every sense organ we possess -- however sophisticated -- is bounded by real functional limits, and understanding these limits is essential to understanding sensation itself.

Our eyes cannot register light stimuli that are extremely dim or extremely bright; our ears cannot register sounds that are extremely faint or extremely loud; and every other sense organ operates within its own comparable working range. In order for any sensory receptor to notice a stimulus at all, that stimulus must be of at least an 'optimal' minimum intensity or magnitude -- this relationship between physical stimuli and the sensations they produce is studied by a branch of psychology called psychophysics.

Two specific measurements describe these limits. The absolute threshold (or absolute limen, AL) is the minimum value a stimulus must reach to activate a given sensory system -- for example, in the classic sugar-water demonstration, a single granule of sugar dissolved in water produces no noticeable sweetness, but as more granules are added one by one, a point is eventually reached where the water is reliably reported as tasting sweet; the number of granules needed to produce this experience on 50% of trials defines the AL for sweetness. Because the AL varies across people, and even for the same person across different occasions (depending on their organic condition and motivational state), it must always be assessed using repeated trials rather than a single observation.

The difference threshold (or difference limen, DL) describes a related but separate limitation -- the smallest difference between two stimuli that is needed before a person can reliably tell that they are different from one another. Continuing the sugar-water example, after the water is already tasting sweet, more granules must be added before the water is judged to taste noticeably sweeter than before; the number of additional granules needed to produce this 'different' judgment on 50% of trials defines the DL for sweetness.

Finally, sensory limitations are not purely about the properties of the stimulus -- the sense organ itself, and the entire neural pathway connecting it to the relevant brain centres, must also be intact. Any structural or functional defect anywhere in this chain -- in the receptor, in the neural pathway, or in the brain area responsible for processing that sensation -- can produce a partial or complete loss of sensation, even when the external stimulus itself is entirely normal.