Visible Spectrum

The visible spectrum is the small part of the electromagnetic spectrum our eyes are tuned to.

Yes! The visible spectrum is composed of wavelengths between 390 to 700 nanometers and each wavelength is associated with a different colour.

No! The visible spectrum is just a small part of the electromagnetic spectrum our eyes are tuned to.

The visible spectrum is associated with the colours red, orange, yellow, green, blue and violet.

The relationship between wavelength and colour is that wavelength is a property of electromagnetic waves whilst human observers see different wavelengths as colours.

Visible light refers to the range of wavelengths of electromagnetic radiation that is perceived as colour by human observers. While the range of visible light is generally considered to be 400-700 nm, the exact range of colours perceptible can vary slightly between individuals.

• Visible light is one form of electromagnetic radiation. Other forms of electromagnetic radiation include radio waves, microwaves, infrared, ultraviolet, X-rays, and gamma rays. Visible light ranges from approximately 400 nanometres (nm) for violet to 700 nm for red.
• A human observer perceives visible light as a combination of all the spectral colours between red and violet, as well as a vast range of other colours produced from the blending of different wavelengths in varying proportions.

Wavelength is the distance from any point on a wave to the corresponding point on the next wave. This measurement is taken along the middle line of the wave.

• While wavelength can be measured from any point on a wave, it is often simplest to measure from the peak of one wave to the peak of the next, or from the bottom of one trough to the bottom of the next, ensuring the measurement covers a whole wave cycle.
• The wavelength of an electromagnetic wave is usually given in metres.
• The wavelength of visible light is typically measured in nanometres, with 1,000,000,000 nanometres making up a metre.
• Each type of electromagnetic radiation – such as radio waves, visible light, and gamma waves – corresponds to a specific range of wavelengths on the electromagnetic spectrum.

A nanometre (nm) is a unit of length in the metric system, equal to one billionth of a metre (1 nm = 1 × 10⁻⁹ metres). It is commonly used to measure extremely small distances, particularly at the atomic and molecular scale.

• In the context of light and electromagnetic radiation, a nanometre is often used to describe wavelengths of visible light.
  The wavelength of visible light ranges from about 700 nm (red) to 400 nm (violet).
• Nanometres are also used to measure components like the thickness of materials, the size of particles in nanotechnology, and the spacing between atoms in a crystal lattice.

The spectral colour model represents the range of pure colours that correspond to specific wavelengths of visible light. These colours are called spectral colours because they are not created by mixing other colours but are produced by a single wavelength of light. This model is important because it directly reflects how human vision perceives light that comes from natural sources, like sunlight, which contains a range of wavelengths.

• The spectral colour model is typically represented as a continuous strip, with red at one end (longest wavelength) and violet at the other (shortest wavelength).
• Wavelengths and Colour Perception: In the spectral colour model, each wavelength corresponds to a distinct colour, ranging from red (with the longest wavelength, around 700 nanometres) to violet (with the shortest wavelength, around 400 nanometres). The human eye perceives these colours as pure because they are not the result of mixing other wavelengths.
• Pure Colours: Spectral colours are considered “pure” because they are made up of only one wavelength. This is in contrast to colours produced by mixing light (like in the RGB colour model) or pigments (in the CMY model), where a combination of wavelengths leads to different colours.
• Applications: The spectral colour model is useful in understanding natural light phenomena like rainbows, where each visible colour represents a different part of the light spectrum. It is also applied in fields like optics to describe how the eye responds to light in a precise, measurable way.

The electromagnetic spectrum includes electromagnetic waves with all possible wavelengths of electromagnetic radiation, ranging from low-energy radio waves through visible light to high-energy gamma rays.

• There are no precisely defined boundaries between the bands of electromagnetic radiation in the electromagnetic spectrum.
• The electromagnetic spectrum includes, in order of increasing frequency and decreasing wavelength: radio waves, microwaves, infrared radiation, visible light, ultraviolet radiation, X-rays and gamma rays.
• Visible light is only a very small part of the electromagnetic spectrum.