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Radiography
Radiography is the creation of images by exposing a photographic film or other image receptor to X-rays. Since X-rays penetrate solid objects, but are weakened by them depending on the object's ... > more -
Electromagnetic spectrum
The electromagnetic spectrum is the range of all possible electromagnetic radiation. Above infrared in frequency comes visible light. This is the range in which the sun and stars similar to it emit ... > more -
Ultrasound
Ultrasound is sound with a frequency greater than the upper limit of human hearing, approximately 20 kilohertz (20,000 hertz). Some animals, such as dogs, dolphins, bats, and mice have an upper limit ... > more -
Hygroscopy
A hygroscopic substance is one that readily attracts water from its surroundings, through either absorption or adsorption. Examples include honey, glycerin, ethanol, methanol, concentrated sulfuric ... > more -
Mobile phone
A mobile phone or cell phone is an electronic telecommunications device with the same basic capability as a conventional fixed-line telephone, but which is also entirely portable and is not required ... > more
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