what connection does the above mentioned measuring unit has with photo?
In photography, the unit for flashes is the watt-second. A flash can be rated in watt-seconds or in joules.
Joule
In photography, the unit for flashes is the watt-second. A flash can be rated in watt-seconds (e.g., 300 W⋅s) or in joules (different names for the same thing), but historically, the term "watt-second" has been used and continues to be used.
where does the sun's luminosity come from Nuclear fusion reactions in its core. can you explain this term you mentioned just now? It is a reaction in which two or more atomic nuclei are combined to form one or more different atomic nuclei and subatomic particles. do this process is experienced by any other planetary body? Stars. in which unit is it measured? Joule. can you mention any one of its characteristic? Luminosity, size, evolution, lifespan, and its eventual fate. what is meant by its binary form? If stars in a binary system are sufficiently close, when one of the stars expands to become a red giant it may overflow its Roche lobe. do they rotate? Yes. comment on its luminosity? It is the amount of light and other forms of radiant energy it radiates per unit of time, it is determined by its radius and surface temperature.
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Joule [SEP] Photography
In photography, the unit for flashes is the watt-second. A flash can be rated in watt-seconds (e.g., 300 W⋅s) or in joules (different names for the same thing), but historically, the term "watt-second" has been used and continues to be used. An on-camera flash, using a 1000 microfarad capacitor at 300 volts, would be 45 watt-seconds. Studio flashes, using larger capacitors and higher voltages, are in the 200–2000 watt-second range. The energy rating a flash is given is not a reliable benchmark for its light output because there are numerous factors that affect the energy conversion efficiency. For example, the construction of the tube will affect the efficiency, and the use of reflectors and filters will change the usable light output towards the subject.