Contents are appropriate for IGCSE Physics

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Definition of Dispersion
Dispersion is the
separation of white
light into a spectrum
by the process of
refraction.

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The cause of dispersion
• Dispersion occurs because different colours
of light travel at slightly different speeds
through transparent substances.
• In glass, perspex and water red travels
quickest, violet slowest.

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Dispersion with a prism
•Violet is deviated the most
•Red is deviated the least

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The spectrum of white light
The numbers are the wavelengths
of the colours in nanometres
where 1 nanometre = 0.000 000 001m.

6. Monochromatic light
• Monochromatic
light is that has one
colour that has been
further broken
down into narrow
wavelengths.
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The rainbow
An example of dispersion
caused by water

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Question 1
Choose appropriate words to fill the gaps in the
paragraph below:
• ____________ occurs when white light is split up into a
____________ by the process of refraction.
• In glass violet light travels more __________ than the
other colours and so is deviated the _________.
• The spectrum consists of red, ________, __________,
_________, ________, indigo and _________.
• A __________ is formed when water causes dispersion.

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Question 2
Explain why
a) orange light is deviated less than blue light in a prism,
b) we know that indigo light travels slower than green
light through water,
c) there are seven colours in the spectrum list.

10. Thank you!
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