# The Visible Spectrum

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## Description

To find out more about the diagram above . . . . read on!

#### The Visible Spectrum

Look carefully at the diagram at the top of the page. Now check out the following questions (and answers)!

1. Is visible light a form of electromagnetic radiation?
2. Name six bands of colour in the visible spectrum starting with red?
3. What is the band of colour with the longest range of wavelengths?
4. What is the band of colour with the shortest range of wavelengths?
5. What is nm the shorthand for? ?

Introducing the diagram! Read back and forward between the image at the top of the page and the explanation below!

This diagram is about sunlight, the visible spectrum and which wavelengths of electromagnetic radiation correspond with the different colours we see in the world.

The diagram shows that wavelengths of light within the visible spectrum correspond with the different colours we see in the world.

Notice that:

• The white arrows in the diagram represent the Sun emitting sunlight at every wavelength of the visible spectrum.
• The term white light is used when all colours of the visible spectrum are mixed together.
• The coloured arrows represent six bands of wavelengths of visible light corresponding with red, orange, yellow, green, blue and violet.
• 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.

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 and on which of those wavelengths are reflected off an object.
• Although a human observer can distinguish between many thousands of wavelengths of light in the visible spectrum our brains often produce the impression of bands of colour.

Follow the blue links for definitions . . . . or check the summaries of key terms below!

#### Some Key Terms

Move to the next level! Check out the following terms.

#### Colour

Things appear coloured because colour corresponds with a property of light that is visible to the human eye. The visual experience of colour is associated with words such as red, blue, yellow, etc.

• The experience of colour is a feature of human vision that depends first of all on the construction of our eyes and the wavelength, frequency and amplitude of visible light that strikes the retina at the back of each eye.
• The human eye, and so human perception, is tuned to the visible spectrum and so to spectral colours between red and violet. It is the sensitivity of the eye to this small part of the electromagnetic spectrum that results in the perception of colour.
• The colour an observer sees depends on the wavelengths of visible light emitted by a light source and on which of those wavelengths are reflected off an object.
• Although a human observer can distinguish between many thousands of wavelengths of light in the visible spectrum our brains often produce the impression of bands of colour.

Electromagnetic radiation is a type of energy that is commonly known as light. Detached from its source, it is transported by electromagnetic waves (or by their quanta, particles called photons) and propagates through space.

• Electromagnetic radiation includes radio waves, microwaves, infrared, (visible) light, ultraviolet, X-rays, and gamma rays.
• All forms of electromagnetic radiation can be described in terms of both waves or particles.
• All forms of electromagnetic radiation travel at 299,792 kilometres per second in a vacuum.

#### Nanometre

A nanometre is a unit of measurement of the wavelength of electromagnetic radiation.

#### Wavelength

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.

#### Slides

• Titles: All slides has titles.
• Backgrounds: Black, framed with a violet gradient.
• Size: 1686 x 1124 pixels (3:2 aspect ratio).
• Slides are available in three file formats: SVG, PNG, AI.

Slides (black backgrounds) are optimized for viewing on screen or with a projector.

Diagrams (white/transparent backgrounds) are optimized for printing on A4 pages in portrait format.

#### Diagrams

• Titles: No titles.
• Backgrounsd SVG: White.
• Backgrounsd PNG: Transparent.
• Backgrounds AI: Fully editable.
• Size: 1686 pixels wide. So all diagrams reproduce at the same scale when inserted into Word documents etc.
• Labels: Calibri 24pt Italic.
• Diagrams are available in three file formats: SVG, PNG, AI.

Diagrams (white/transparent backgrounds) are optimized for printing on A4 pages in portrait format.

Slides (black backgrounds) are optimized for viewing on screen or using a projector.

#### SVG file format

• Text on SVG images with black backgrounds has been converted from fonts to outlines.
• Text on SVG images with white (or transparent) backgrounds use Calibri 24pt Italic.

Did you know:

• SVG (.svg) stands for Scalable Vector Graphic.
• SVG files scale up or down without loss of definition because they are like line drawings.
• SVG files are much smaller in size than most other file formats (e.g JPEG or PNG).
• You can insert SVG files directly into MS Word 365 or PowerPoint 365.
• You can view SVG files by dragging the file into a browser tab.
• You can edit SVG files using programs such as Adobe Illustrator.

#### PNG file format

• Because all images are a standard width they reproduce consistently on an A4 page.

Did you know:

• PNG (.png) stands for Portable Network Graphics.
• PNG files are raster files as are JPG’s (.jpeg) files, so they behave like photos.
• Our PNG’s are 32bit files.
• You can insert or paste PNG’s directly into MS Word 365 or PowerPoint 365.
• You can view PNG files by dragging them into a browser tab.
• You can edit PNG files using programs such as Adobe Photoshop.