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  2. List of reagent testing color charts - Wikipedia

    en.wikipedia.org/wiki/List_of_reagent_testing...

    It is advised to check the references for photos of reaction results. [1] Reagent testers might show the colour of the desired substance while not showing a different colour for a more dangerous additive. [2]

  3. Emergency vehicle lighting - Wikipedia

    en.wikipedia.org/wiki/Emergency_vehicle_lighting

    The three emergency lights used in Romania are red, blue and amber. At a red flashing light, bringing the vehicle to a full stop is compulsory, while for a blue light yielding, slowing down and moving out of the way is compulsory, and an amber light means other traffic vehicles must proceed with caution due to an oversized or slow vehicle.

  4. Navigation light - Wikipedia

    en.wikipedia.org/wiki/Navigation_light

    Watercraft navigation lights must permit other vessels to determine the type and relative angle of a vessel, and thus decide if there is a danger of collision. In general, sailing vessels are required to carry a green light that shines from dead ahead to 2 points (22 + 1 ⁄ 2 °) abaft [note 1] the beam on the starboard side (the right side from the perspective of someone on board facing ...

  5. Green flash - Wikipedia

    en.wikipedia.org/wiki/Green_flash

    Green flash occurs because the atmosphere causes the light from the Sun to separate, or refract, into different frequencies. Green flashes are enhanced by mirages, which increase refraction. A green flash is more likely to be seen in stable, clear air, when more of the light from the setting sun reaches the observer without being scattered.

  6. Variations in traffic light operation - Wikipedia

    en.wikipedia.org/wiki/Variations_in_traffic...

    Variations on the protected/permissive traffic signals in the United States; (1) is the "classic" doghouse five-light signal introduced in 1971; (2) and (3) incorporate flashing yellow arrows. In the US, a flashing yellow arrow is a signal phasing configuration for permissive left turns.

  7. Satellite flare - Wikipedia

    en.wikipedia.org/wiki/Satellite_flare

    Satellite flare, also known as satellite glint, is a satellite pass visible to the naked eye as a brief, bright "flare".It is caused by the reflection toward the Earth below of sunlight incident on satellite surfaces such as solar panels and antennas (e.g., synthetic aperture radar).