# Wavelengths from Red to Violet

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This diagram is about which wavelengths of electromagnetic radiation correspond with the different colours we see in the world.

The important fact to remember is that the wavelengths of light within the visible spectrum correspond with all the colours that we see between red and violet.

• The white arrows in the diagram show the Sun emitting sunlight at all wavelengths of the visible spectrum.
• The term white light is used when all colours of the visible spectrum are mixed together.
• The spectrum of colours between red and violet illustrates that although an observer will often describe visible light (a rainbow for example) as six bands of colour, each and every wavelength between 700 and 430 nanometres is a different colour.
• The list on the left shows the range of wavelengths corresponding with each band of colour.
• The red arrow, for example, corresponds with wavelengths between 700 nanometres and 620 nanometres. Red is the colour an observer sees if any wavelength in that range strikes a neutral coloured surface.
• The scale along the bottom is marked in nanometres and shows the visible spectrum divided into coloured bands.
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## Description

#### Wavelengths from Red to Violet

###### TRY SOME QUICK QUESTIONS AND ANSWERS TO GET STARTED
nm is shorthand for nanometre.
Infrared and ultraviolet are forms of electromagnetic radiation with wavelengths just outside the visible spectrum.
Wavelengths visible to the eye are in a band between approximately 390 to 700 nanometres.
Yes! The wavelengths of colours in the visible spectrum are measured in nanometres.

• This diagram is about which wavelengths of electromagnetic radiation correspond with the different colours we see in the world.
• The important fact to remember is that the wavelengths of light within the visible spectrum correspond with the spectral colours we see between red and violet.
• The white arrows in the diagram show the Sun emitting sunlight at all wavelengths of the visible spectrum.
• The term white light is used when all wavelengths and the colours of the visible spectrum are mixed together.
• The full spectrum of colours between red and violet illustrates that each and every wavelength between 700 and 430 nanometres produces a different colour.
• The list on the left shows the ranges of wavelengths that correspond with the most prominent spectral colours
• The scale along the bottom is marked in nanometres and shows the visible spectrum divided into coloured bands.
###### Remember that:
• Objects appear to be different colours to an observer depending on their wavelength.
• The name given to light that contains all wavelengths of the visible spectrum is white light.
• When all wavelengths contained in white light reflect off a neutral-coloured surface then the object appears white to an observer.
• When a narrow band of wavelengths reflect off a neutral-coloured surface then the object appears coloured to an observer.
• The colour an observer sees depends on:
• The wavelengths of visible light emitted by a light source.
• The wavelengths absorbed or reflected off an object.
• Although a human observer can distinguish between many thousands of wavelengths of light in the visible spectrum, the impression is often of predominant bands of colour.

#### Some key terms

Sunlight is light emitted by the Sun and is also called daylight or visible light.

• Sunlight is only one form of electromagnetic radiation emitted by the Sun.
• Sunlight is only a very small part of the electromagnetic spectrum.
• Sunlight is the form of electromagnetic radiation that our eyes are sensitive to.
• Other types of electromagnetic radiation that we are sensitive to, but cannot see, are infrared radiation that we feel as heat and ultraviolet radiation that causes sunburn.

Wavelength is a measurement from any point on the path of a wave to the same point on its next oscillation. The measurement is made parallel to the centre-line of the wave.

• The wavelength of an electromagnetic wave is measured in metres.
• Each type of electromagnetic radiation, such as radio waves, visible light and gamma waves,  forms a band of wavelengths on the electromagnetic spectrum.
• The visible part of the electromagnetic spectrum is composed of the range of wavelengths that correspond with all the different colours we see in the world.
• Human beings don’t see wavelengths of visible light, but they do see the spectral colours that correspond with each wavelength and the other colours produced when different wavelengths are combined.
• The wavelength of visible light is measured in nanometres. There are 1,000,000,000 nanometres to a metre.

Electromagnetic radiation refers to the transfer of all forms of radiation through space by electromagnetic waves.

• Electromagnetic radiation includes gamma rays, ultraviolet (UV), infrared (IR), X-rays, and radio waves, as well as visible light.
• Detached from its source, electromagnetic radiation (EM radiation), is transported by electromagnetic waves (or their quanta, photons) and propagates through empty space at the speed of light.
• Man-made technologies that produce electromagnetic radiation include radio and TV transmitters, radar, MRI scanners, microwave ovens, computer screens, mobile phones, all types of lights and lamps, electric blankets, electric bar heaters, lasers and x-ray machines.

White light is the name given to visible light that contains all wavelengths of the visible spectrum at equal intensities.

• As light travels through a vacuum or a medium it is described as white light if it contains all the wavelengths of visible light.
• As light travels through the air it is invisible to our eyes.
• When we look around we see through the air because it is very transparent and light passes through it.
• The term white light doesn’t mean light is white as it travels through the air.
• One situation in which light becomes visible is when it reflects off the surface of an object.
• When white light strikes a neutral coloured object and all wavelengths are reflected then it appears white to an observer.

The perception of colour by an observer results from properties of light that are visible to the human eye. The visual experience of colour is associated with terms like red, blue and yellow.

• The observation of colour depends on:
• The range and intensity of wavelengths of visible light emitted by a light source, and the various media and materials it encounters on its journey to the retina of a human eye
• Optical phenomena such as absorption, dispersion, diffraction, polarization, reflection, refraction, scattering and transmission.
• Predispositions of an observer, such as their personal and social experience, health and state of mind.

Visible light is the range of wavelengths of electromagnetic radiation perceived as colour by human observers.

• Visible light is a form of electromagnetic radiation.
• Other forms of electromagnetic radiation include radio waves, microwaves, infrared, ultraviolet, X-rays, and gamma rays.
• Visible light is perceived by a human observer as all the spectral colours between red and violet plus all other colours that result from combining wavelengths together in different proportions.
• A spectral colour is produced by a single wavelength of light.
• The complete range of colours that can be perceived by a human observer is called the visible spectrum.
• The range of wavelengths that produce visible light is a very small part of the electromagnetic spectrum.

The visible part of the electromagnetic spectrum is called the visible spectrum.

• The visible spectrum is the range of wavelengths of the electromagnetic spectrum that correspond with all the different colours we see in the world.
• As light travels through the air it is invisible to our eyes.
• Human beings don’t see wavelengths of light, but they do see the spectral colours that correspond with each wavelength and colours produced when different wavelengths are combined.
• The visible spectrum includes all the spectral colours between red and violet and each is produced by a single wavelength.
• The visible spectrum is often divided into named colours, though any division of this kind is somewhat arbitrary.
• Traditional colours referred to in English include red, orange, yellow, green, blue, and violet.