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Unfortunately, Io did not turn out to be a good clock. Not local time, which was already possible, but a "universal" time that would be the same for all observers on the Earth, Knowing the standard time would allow one to determine one's longitude on the Earth - a handy thing to know when navigating the featureless oceans. Rømer's idea was to use the transits of Jupiter's moon Io to determine the time. Roemer de l'Académie des Sciences." Journal des Scavans. "Démonstration touchant le mouvement de la lumière trouvé par M. In fact I have tried the experiment only at a short distance, less than a mile, from which I have not been able to ascertain with certainty whether the appearance of the opposite light was instantaneous or not but if not instantaneous it is extraordinarily rapid…. Veramente non l'ho sperimentata, salvo che in lontananza piccola, cioè manco d'un miglio, dal che non ho potuto assicurarmi se veramente la comparsa del lume opposto sia instantanea ma ben, se non instantanea, velocissima…. The speed of light in a vacuum is represented by the letter c from the Latin celeritas - swiftness. Shrimpo­luminescence: pistol shrimp, mantis shrimp Photoluminescence whose radiation is located in a spectral region of shorter wavelengths than that of the exciting radiationĬaused by imploding bubbles in a liquid formed by sound waves Luminescence caused by the impact of electrons on certain types of luminescent materials, such as the coating on a television screenĮmitted radiation has a shorter wavelength than the absorbed radiation Thermally activated luminescence luminescence occurring when a previously excited luminescent material is heatedĬRT displays in 20th century TVs and computers Occurs when a previously excited material is heated Occurs when a solid is under changing mechanical stress Luminescence caused by the action of mechanical forces Peeling transparent tape, biting Wint-O-Green Life Savers Occurs when a solid is rubbed or scratched (or ripped or crushed) Luminescence caused by energy released by a chemical reactionĬhemiluminescence occurring in living organisms Luminescence caused by x-rays or radioactive radiationĬaused by energy released in a chemical reaction Luminescence caused by the action of an electric field in a gas or in a solid materialĬaused by the absorption of x-rays or radioactive radiation Some outdoor advertising, some nightlights Technically, the term "phosphorescence" should be used only for the delayed emission due to a "forbidden transition" from an excited triplet state to a ground singlet state.Ĭaused by the action of an electric field Fluorescence is due to an "allowed" transition generally from an excited singlet state to a ground singlet state.Įmission is "delayed" after excitation by more than 10 nsĭelayed emission of optical radiation which appears 10 ns or longer after the excitation. Radiation is emitted within 10 ns of excitationĮmission of optical radiation when a substance is exposed to any type of electromagnetic radiation, where the emitted radiation generally appears within 10 ns after the excitation. Luminescence caused by absorption of optical radiation

Includes fluorescence and phosphorescence Types of luminescence with special names typeĬaused by absorption of optical radiation (IR, light, UV) (in matter that may or may not be "hot").

The transverse nature of light can be demonstrated through polarization.

Like all electromagnetic waves, light can travel through a vacuum. The wave nature of light was first illustrated through experiments on diffraction and interference. Light is a transverse, electromagnetic wave that can be seen by the typical human.