Rainbow in the context of "Nebra sky disc"

In optics, a dispersive prism is an optical prism that is used to disperse light, that is, to separate light into its spectral components (the colors of the rainbow). Different wavelengths (colors) of light will be deflected by the prism at different angles. This is a result of the prism material's index of refraction varying with wavelength (dispersion). Generally, longer wavelengths (red) undergo a smaller deviation than shorter wavelengths (blue). The dispersion of white light into colors by a prism led Sir Isaac Newton to conclude that white light consisted of a mixture of different colors.

Triangular prisms are the most common type of dispersive prism. Other types of dispersive prism exist that have more than two optical interfaces; some of them combine refraction with total internal reflection.

A spectrum (pl.: spectra or spectrums) is a set of related ideas, objects, or properties whose features overlap such that they blend to form a continuum. The word spectrum was first used scientifically in optics to describe the rainbow of colors in visible light after passing through a prism. In the optical spectrum, light wavelength is viewed as continuous, and spectral colors are seen to blend into one another smoothly when organized in order of their corresponding wavelengths. As scientific understanding of light advanced, the term came to apply to the entire electromagnetic spectrum, including radiation not visible to the human eye.

Spectrum has since been applied by analogy to topics outside optics. Thus, one might talk about the "spectrum of political opinion", or the "spectrum of activity" of a drug, or the "autism spectrum". In these uses, values within a spectrum may not be associated with precisely quantifiable numbers or definitions. Such uses imply a broad range of conditions or behaviors grouped together and studied under a single title for ease of discussion. Nonscientific uses of the term spectrum are sometimes misleading. For instance, a single left–right spectrum of political opinion does not capture the full range of people's political beliefs. Political scientists use a variety of biaxial and multiaxial systems to more accurately characterize political opinion.

In physics, refraction is the redirection of a wave as it passes from one medium to another. The redirection can be caused by the wave's change in speed or by a change in the medium. Refraction of light is the most commonly observed phenomenon, but other waves such as sound waves and water waves also experience refraction. How much a wave is refracted is determined by the change in wave speed and the initial direction of wave propagation relative to the direction of change in speed.

Optical prisms and lenses use refraction to redirect light, as does the human eye. The refractive index of materials varies with the wavelength of light, and thus the angle of the refraction also varies correspondingly. This is called dispersion and allows prisms and raindrops in rainbows to divide white light into its constituent spectral colors.

An optical prism is a transparent optical element with flat, polished surfaces that are designed to refract light. At least one surface must be angled—elements with two parallel surfaces are not prisms. The most familiar type of optical prism is the triangular prism, which has a triangular base and rectangular sides. Not all optical prisms are geometric prisms, and not all geometric prisms would count as an optical prism. Prisms can be made from any material that is transparent to the wavelengths for which they are designed. Typical materials include glass, acrylic and fluorite.

A dispersive prism can be used to break white light up into its constituent spectral colors (the colors of the rainbow) to form a spectrum as described in the following section. Other types of prisms noted below can be used to reflect light, or to split light into components with different polarizations.

A soap bubble (commonly referred to as simply a bubble) is an extremely thin film of soap or detergent and water enclosing air that forms a hollow sphere with an iridescent surface. Soap bubbles usually last for only a few seconds before bursting, either on their own or on contact with another object. They are often used for children's enjoyment, but they are also used in artistic performances. Assembling many bubbles results in foam.

When light shines onto a bubble it appears to change colour. Unlike those seen in a rainbow, which arise from differential refraction, the colours seen in a soap bubble arise from light wave interference, reflecting off the front and back surfaces of the thin soap film. Depending on the thickness of the film, different colours interfere constructively and destructively.

The Grand Prismatic Spring in Yellowstone National Park is the largest hot spring in the United States, and the third largest in the world, after Frying Pan Lake in New Zealand and Boiling Lake in Dominica. It is located in the Midway Geyser Basin.

Grand Prismatic Spring was noted by geologists working in the Hayden Geological Survey of 1871, and named by them for its striking coloration. Its colors match most of those seen in the rainbow dispersion of white light by an optical prism: red, orange, yellow, green, and blue.

A leprechaun (Irish: lucharachán/leipreachán/luchorpán) is a diminutive supernatural being in Irish folklore, classed by some as a type of solitary fairy. They are usually depicted as little bearded men, wearing a coat and hat, who partake in mischief. In later times, they have been depicted as shoe-makers who have a hidden pot of gold at the end of the rainbow.

Leprechaun-like creatures rarely appear in Irish mythology and only became prominent in later folklore.

The fundamental practice of Vajrayana and Tibetan tantra is deity yoga (devatayoga), a form of Buddhist meditation centered on a chosen deity or "cherished divinity" (Skt. Iṣṭa-devatā, Tib. yidam). This involves the recitation of mantras and prayers alongside the detailed visualization of the deity and their mandala—a sacred configuration that includes their Buddha field, consorts, and attendant figures. The 14th-century scholar Tsongkhapa stated that deity yoga is the distinctive feature that sets Tantra apart from the Sutra-based path.

In the highest class of Tantras, the Unsurpassed Yoga Tantras, deity yoga is typically practiced in two stages: the generation stage (utpatti-krama) and the completion stage (nispanna-krama). In the generation stage, practitioners dissolve ordinary perception into emptiness and then re-imagine reality through the form of a fully enlightened deity, understood as an expression of ultimate truth. The deity is visualized as “empty yet apparent,” like a mirage or rainbow, never solid or objectively real.

The rainbow flag or pride flag (formerly gay pride flag) is a symbol of LGBTQ pride and LGBTQ social movements, as well as a peace symbol. The colors reflect the diversity of the LGBTQ community and the spectrum of human sexuality and gender. Using a rainbow flag as a symbol of LGBTQ pride began in San Francisco, California and subsequently became common at LGBTQ rights events worldwide.

Originally devised by the artists Gilbert Baker, Lynn Segerblom, James McNamara and other activists, the design underwent several revisions after its debut in 1978, and continues to inspire variations. Although Baker's original rainbow flag had eight colors, from 1979 to the present day the most common variant consists of six stripes: red, orange, yellow, green, blue, and violet. The flag is typically displayed horizontally, with the red stripe on top, as it would be in a natural rainbow.