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Most liquids and aqueous solutions are highly transparent. For example, water, cooking oil, rubbing alcohol, air, and natural gas are all clear. Absence of structural defects (voids, cracks, etc.) and molecular structure of most liquids are chiefly responsible for their excellent optical transmission.
Iridescence is also found in plants, animals and many other items. The range of colours of natural iridescent objects can be narrow, for example shifting between two or three colours as the viewing angle changes, [5] [6] An iridescent biofilm on the surface of a fish tank diffracts the reflected light, displaying the entire spectrum of colours ...
An opaque object is neither transparent (allowing all light to pass through) nor translucent (allowing some light to pass through). When light strikes an interface between two substances, in general, some may be reflected, some absorbed, some scattered, and the rest transmitted (also see refraction).
The gas inside a bubble is less dense than air because it is mostly water vapor. Water vapor is a gas that is formed when water molecules evaporate. When water molecules evaporate, they escape from the liquid state and enter the gas state. In the gas state, water molecules are further apart than they are in the liquid state.
The earliest known glass objects were beads, perhaps created accidentally during metalworking or the production of faience, which is a form of pottery using lead glazes. Due to its ease of formability into any shape, glass has been traditionally used for vessels, such as bowls , vases , bottles , jars and drinking glasses.
These crystals were formed into a large solid cone for transport and sale. This solid sugar cone had to be broken into usable chunks using a sugar nips device. People began to notice that tiny bursts of light were visible as sugar was "nipped" in low light, an established example of triboluminescence. [6]
The simplest kind of cyanotype print is a photogram, made by arranging objects on sensitised paper. Fresh or pressed plants are a typical subject but any opaque to translucent object will create an image. A sheet of glass will press flat objects into close contact with the paper, resulting in a sharp image.
Familiar examples are the upward flow of air due to a fire or hot object and the circulation of water in a pot that is heated from below. Forced convection: when a fluid is forced to flow over the surface by an internal source such as fans, by stirring, and pumps, creating an artificially induced convection current. [3]