| E.M.
Spectrum (uses, dangers, sources, production) - and wave equation
relationship |
PHY1H |
| 11.5
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What
are the uses and
hazards of the waves that form the electromagnetic
spectrum?
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Electromagnetic
radiations are disturbances in an electric field. They travel as
waves and move energy from one place to another. They can all travel
through a vacuum and do so at the same speed. The waves cover a
continuous range of wavelengths called the electromagnetic spectrum.
The uses and hazards of the radiations in different parts of the
electromagnetic spectrum depend on their wavelength and frequency.
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Candidates
should use
their skills, knowledge and
understanding of how science
works:
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• to evaluate the possible hazards associated with the use of different
types of electromagnetic radiation |
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• to evaluate methods to reduce exposure to different types of electromagnetic
radiation. |
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Their
skills, knowledge and
understanding of how science
works should be set in these
substantive contexts:
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• Electromagnetic radiation travels as waves and moves energy from
one place to another. |
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• All types of electromagnetic waves travel at the same speed through
a vacuum (space). |
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• The electromagnetic spectrum is continuous but the wavelengths within
it can be grouped into types of increasing wavelength and decreasing
frequency:
– gamma rays, X-rays, ultraviolet rays, visible light, infra
red rays, microwaves and radio waves. |
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• Different wavelengths of electromagnetic radiation are reflected,
absorbed or transmitted differently by different substances and
types of surface. |
Reflection and refraction need to be revised from KS3 here |
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• When radiation is absorbed the energy it carries makes the
substance which absorbs it hotter and may create an alternating
current with the same frequency as the radiation itself.
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Link
to work on heat travel
This is how a radio aerial works |
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• Different wavelengths of electromagnetic radiation have different
effects on living cells. Some radiations mostly pass through soft
tissue without being absorbed, some produce heat, some may cause
cancerous changes and some may kill cells. These effects
depend on the type of radiation and the size of the dose. |
Ionizing
radiation can cause mutations in DNA |
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• The
uses and the hazards associated with the use of each type of radiation
in the electromagnetic spectrum.
- Radiowaves,
microwaves, infra red and visible light can be used for communication.
- Microwaves can pass through the Earth's atmosphere and are used
to send information to and from satellites and within mobile phone
networks.
- Infra red and visible light can be used to send signals along
optical fibres and so travel in curved paths.
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Reflection
and refraction and an extension of this into TIR will be done here
to explain optical fibres more thoroughly |
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• Communication signals may be analogue
(continuously
varying) or digital (only on and off). Digital signals
are less prone to interference than analogue and can be processed
by computers. |
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• Electromagnetic waves obey the wave formula:
wave speed (metre/second, m/s) = frequency (hertz, Hz) × wavelength
(metre, m)
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This
requires calculation work |