key words
amplitude |
is half of the distance between a waves high point crest and low point trough. Amplitude measures how much a wave is displaced from its resting point. |
wavelength |
is measured from a point on one wave to the same point on the next wave and is written as λ (Greek letter for lamba). The difference in colours is caused by different wavelengths of light. Red has the longest wavelength in the rainbow while purple has the shortest |
oscillation |
an up-and-down or back-and-forth motion |
vacuum |
space that has no matter in it |
frequency |
the number of waves that pass a fixed point in a given unit of time is written as f |
node |
the node of a wave is where the wave doesn't move |
antinode |
the part of the wave where it moves the most away from the centre |
wave speed |
is the speed at which the energy is transferred through the medium |
transverse Wave |
are when the oscillations are perpendicular to the direction of the waves advance |
longitudinal wave |
are when the displacement is parallel to the direction of the wave |
overtone |
generally applied to any higher-frequency standing wave |
fundamental |
the frequency at which the entire wave vibrates |
stationary waves |
when two waves are moving at the same time in opposite directions, both having the same amplitude and frequency |
Displacement |
how far the quantity that is in oscillation has moved from its mean |
Period |
time taken for a wave to pass |
electromagnetic |
is a continuous range of wavelengths electro contains electric energy magnetic contains magnetic disturbance** |
phase difference |
The difference in phase angle of two different waves with the same frequency |
equations
frequency = 1/time or time = frequency/1 |
f=1/t or T=f/1 |
speed= frequency x wavelength |
v=f x λ |
wavespeed = frequency x wavelength |
v=f x λ |
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electromagnetic spectrum
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uses |
dangers |
radio waves (3x109) |
Telecommunication, TV, radio |
None |
microwaves (3x1012) |
Cooking, telecommunication, RADAR |
None |
infra red radiation (4x1014) |
Heating, cooking, TV remotes, night vision |
Can burn |
visible light (10-6) |
photography, illumination |
erythema, pigmentation, thermal damage, free radical, production |
ultra violet (10-9) |
killing bacteria, creating fluorescent effects, curing inks and resins, phototherapy, sun tanning, security |
skin cancer, premature ageing |
X-rays (10-6) |
looks at bones |
causes cancer |
gamma rays (10-4) |
radio therapy, sterilisation and disinfection, nuclear industry |
Causes cancer |
the laws of refraction
Light waves (or electromagnetic radiation of other frequencies) travel best in a vacuum (a space without any matter in it) |
When the waves have to travel through solid, opaque materials, their movement IS STOPPED by the electronic charges of the atoms and molecules around them e.g Metals that are full of freely moving electrons stop the oscillations completely and so the light wave energy is reflected back – metals therefore look shiny and make good mirrors. Some waves are absorbed in solids, with certain waves being reflected back so that we are able to see colours |
In transparent materials (water, glass and many plastics) the waves are NOT STOPPED or ABSORBED but they are slowed down |
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