General Physics

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The density of dry air is more than that of moist air (when moisture is removed from air, its density increases). The speed of sound in a medium is inversely proportional to the square root of its density. Therefore, the speed of sound in moist air is more than that in dry air.

Scintillation or twinkling is generic terms for variations in apparent brightness or position of a distant luminous object viewed through a medium. If the object lies outside the Earth’s atmosphere, as in the case of stars and planets, the phenomenon is termed astronomical scintillation; within the atmosphere, the phenomenon is termed terrestrial scintillation

The ozone layer absorbs 97–99% of the Sun’s medium-frequency ultraviolet light (from about 200 nm to 315 nm wavelength), which potentially damages exposed life forms on Earth. Ozone is formed from di-oxygen by the action of ultraviolet light and also atmospheric electrical discharges, and is present in low concentrations throughout the Earth’s atmosphere. In total, ozone makes up only 0.6 parts per million of the atmosphere.

The central mass of the sun becomes increasingly hot and dense, eventually initiating thermonuclear fusion in its core. It is thought that almost all other stars form by this process. nuclear fusion is a nuclear reaction in which two or more atomic nuclei join together, or “fuse”, to form a single heavier nucleus.

The decibel (abbreviated dB) is the unit used to measure the intensity of a sound. The decibel scale is a little odd because the human ear is incredibly sensitive. Our ears can hear everything from your fingertip brushing lightly over your skin to a loud jet engine.

Nuclear fusion is a nuclear reaction in which two or more atomic nuclei join together, or “fuse”, to form a single heavier nucleus. During this process, matter is not conserved because some of the mass of the fusing nuclei is converted to energy which is released. Fusion is the process that powers active stars.

Sonar (originally an acronym for Sound Navigation And Ranging) is a technique that uses sound propagation (usually underwater, as in submarine navigation) to navigate, communicate with or detect objects on or under the surface of the water, such as other vessels.

In summer, when the barometer falls suddenly, a thunderstorm can be expected, and if it does not rise again upon its cessation, the weather will probably continue unsettled for several days. In summer, when a thunderstorm happens, there is little or no depression of the barometer.