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Flicker vertigo, sometimes called the Bucha effect, is "an imbalance in brain-cell activity caused by exposure to low-frequency flickering (or flashing) of a relatively bright light." [ 1 ] It is a disorientation -, vertigo -, and nausea -inducing effect of a strobe light flashing at 1 Hz to 20 Hz, approximately the frequency of human brainwaves .
In other words, it is the opposite to a flashing light where the total duration of darkness is longer than the duration of light. It has the appearance of flashing off, rather than flashing on. Like a flashing light, it can be used for a single occulting light that exhibits only a single period of darkness or the periods of darkness can be ...
An embedded flashing-light system, or an in-pavement flashing-light system, is a traffic safety device installed at pedestrian crossings or intersections to enhance driver awareness of pedestrians or traffic signals. These systems typically consist of LED lights embedded within the road surface, positioned to face oncoming traffic or pedestrians.
A sprite at the horizon, with lightning below in the troposphere and above the green line of airglow at the upper mesopause and border to space (the bright light above is the Moon). First color image of a sprite, taken from an aircraft
The yellow trap occurs when the timing of the amber lights (also known as "yellow" lights in the USA) is asymmetric for two-way traffic on a single road: when a vehicle is waiting to turn across oncoming traffic and receives an amber light from the traffic signal, the driver may assume that oncoming traffic also has received an amber light and ...
In New Zealand, where traffic is on the left, when a road is given a green light from an all-direction stop, a red arrow can continue to display to turning traffic, holding traffic back while a pedestrian crossing on the side road is given a green signal (for left turns) or while oncoming traffic goes straight ahead and there is no permissive right turn allowed (for right turns).
Photopsia is the presence of perceived flashes of light in the field of vision. It is most commonly associated with: [4] posterior vitreous detachment; migraine aura (ocular migraine / retinal migraine) migraine aura without headache; scintillating scotoma; retinal break or detachment; occipital lobe infarction (similar to occipital stroke)
Crepuscular rays are noticeable when the contrast between light and dark is most obvious. Crepuscular comes from the Latin word crepusculum, meaning "twilight". [2] Crepuscular rays usually appear orange because the path through the atmosphere at dawn and dusk passes through up to 40 times as much air as rays from a high Sun at noon.