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The periodic (daily) exposure to sunlight generally tunes the circadian rhythm to a 24-hour cycle. However, exposure to light sources that excite melanopsin in the retina during nighttime can interfere with the circadian rhythm. Harvard Health Publishing asserts that exposure to blue light at night has a strong negative effect on sleep. [17]
The length of light exposure influences entrainment. Longer exposures have a greater effect than shorter exposures. [12] Consistent light exposure has a greater effect than intermittent exposure. [14] In rats, constant light eventually disrupts the cycle to the point that memory and stress coping may be impaired. [15]
The widespread use of blue light in modern technology brings up a concern about the potential consequences of excessive blue light exposure. [4] Such exposure has been associated with disruptions in ocular health, sleep patterns, and well-being.
Light therapy, also called phototherapy or bright light therapy is the exposure to direct sunlight or artificial light at controlled wavelengths in order to treat a variety of medical disorders, including seasonal affective disorder (SAD), circadian rhythm sleep-wake disorders, cancers, neonatal jaundice, and skin wound infections.
This is in some cases the mechanism used for glow-in-the-dark materials which are "charged" by exposure to light. Unlike the relatively swift reactions in fluorescence, such as those seen in laser mediums like the common ruby , phosphorescent materials "store" absorbed energy for a longer time, as the processes required to reemit energy occur ...
The use of radiometric units is appropriate to characterize such sensitivity to invisible light. In sensitometric data, such as characteristic curves, the log exposure [4] is conventionally expressed as log 10 (H). Photographers more familiar with base-2 logarithmic scales (such as exposure values) can convert using log 2 (H) ≈ 3.32 log 10 (H).
Digital TTL works as follows: Before the actual exposure one or more small flashes, called "preflashes", are emitted. The light returning through the lens is measured and this value is used to calculate the amount of light necessary for the actual exposure. Multiple pre-flashes can be used to improve the flash output.
Phytophotodermatitis may be aggravated by the additional levels of ultraviolet light emitted by compact fluorescent light. Patients undergoing photodynamic therapy are at additional risk of adverse photosensitive reactions caused by compact fluorescent light. One cause of cataracts is exposure to ultraviolet light. Provided the level of UV ...