Opaque substances that are used to color other materials are called pigments. Some call them dyes.
pigments
pigments
OPAQUE is the word that describes an object or substance that blocks light (or other energy form). TRANSLUCENT describes objects that allow transmission of light, but scatter it from the original form or direction. TRANSPARENT describes objects that allow the passage of light, usually optically clear substances such as glass.
Reflects, other wavelengths (colours) are absorbed.
Materials which do not allow the transmission of light are called opaque. These substances have chemical compositions, some of which are referred to as absorption centers. This means that the material absorbs all of the light wave frequencies, not just some while reflecting other frequencies.
A material through which light (or a certain color of light) won't pass through is said to be OPAQUE for light (or for that color of light). Most materials around us are opaque for visible light; only a few materials, such as air and other gases, water, and glass, are transparent, meaning they do let light through.
materials usually expand when heated.
Impenetrable by light; neither transparent nor translucent.Not reflecting light; having no luster: an opaque finish...Impenetrable by a form of radiant energy other than visible light: a chemical solution opaque to x-rays..So obscure as to be unintelligible: "opaque, elusive, minimal meanings" .Obtuse of mind; dense. See synonyms at dark...Opaque materials are materials that you cannot see things through it..Add Me AuBrEy ZyRenE SolAs EnTrInA
wood Think of any material that you cannot see through. Steel, Concrete, Granite,... These are opaque: Light does not pass from one side to the other. Examples of materials that are not opaque: Water, Glass, Air [a mixture of gases]
wood, metal and other substances.
pigments are colored substances that are used to mcolor other materials.
A converging (convex) lens will produce a shadow with the focal point in the center.