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Trapezoid is a convex quadrilateral with only one pair of parallel sides. The parallel sides are called the bases of the trapezoid and the other two sides ... more

The Doppler effect is the change in frequency of a wave (or other periodic event) for an observer moving relative to its source. When the speeds of source ... more

The photoelectric effect is the observation that many metals emit electrons when light shines upon them. Electrons emitted in this manner may be called ... more

The Stanton number, St, is a dimensionless number that measures the ratio of heat transferred into a fluid to the thermal capacity of fluid. The Stanton ... more

Pulse tube cryocooler(or refrigerator) can be made without moving parts in the low temperature part of the device, making the cooler suitable for a wide ... more

In optics, the f-number (sometimes called focal ratio, f-ratio, f-stop, or relative aperture) of an optical system is the ratio of the lens’s focal ... more

Pressure altitude within the atmosphere is the altitude in the International Standard Atmosphere with the same pressure as the part of the atmosphere in ... more

Pressure altitude within the atmosphere is the altitude in the International Standard Atmosphere with the same pressure as the part of the atmosphere in ... more

In fluid flow, friction loss (or skin friction) is the loss of pressure or “head” that occurs in pipe or duct flow due to the effect of the fluid’s ... more

The Doppler effect is the change in frequency of a wave (or other periodic event) for an observer moving relative to its source. When the speeds of source ... more