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physics waves revision

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
 

electr­oma­gnetic spectrum

 
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

Diagrams

   
 

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