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Flashcards in Waves Deck (26)
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What is the order of waves?

radio, microwaves, infrared, visible, ultraviolet, x-ray, gamma


What is a transverse wave?

the oscillations are at right angles to the direction the waves are travelling (s-shape)


What is a longitudinal wave?

the oscillations are parallel to the travelling direction (backwards and forwards)


what type of wave are:
- electromagnetic
- sound waves
- water waves?

transverse, longitudinal, transverse (actually a combination)


what is amplitude?
measured in?

maximum displacement from the equilibrium position of the substance the wave is moving in
metres (m)


what is frequency?
symbol + measured in?

number of complete wave cycles in 1 second
f; hertz (Hz)


what is wavelength?
symbol and measured in?

distance from one point on a wave to the next identical point on the next wave
λ; metres (m)


what's the period of a wave?

T; time taken for the source to produce one complete wave (in seconds)


what's an oscillation

repetitive to and fro movement


what is it in a wave that oscillates?

the medium it is travelling through


what's the formula linking wave speed, frequency and wavelength?

v = f x λ


what's the formula for frequency & the time period?

f = 1 ÷ T


what rule links the angle i and the angle r in light rays reflecting?

i = r


where are the i and r angles?

between the reflected / incident ray and the normal


how do plane waves reflect off a concave (curving in) barrier?

- waves more curved than the barrier
- brought to a focus
- no change in wavelength


how do circular waves reflect off a plane (flat) barrier?

- waves appear to be coming from a virtual source as far behind the barrier as the true source is in front
- no change in wavelength


what does the speed of a wave depend on?

the properties of the medium it is travelling through


what can the change of speed at a boundary cause?
how can you tell the speed has changed?

a change of direction of travel at the boundary (refraction)
the waves will bunch up / space out


where does the light bend when travelling from air into glass?

towards the normal


what does frequency have to do

stay the same


what happens if the waves cross the boundary at right angles?

no change of direction


radio waves facts (2)

- produced and transmitted by very rapidly alternating electric currents
- received by aerials where the those currents are induced by the radio waves


microwaves facts (6)

- wavelengths range from mm to cm
- can cook things containing water
- the water molecules become agitated because their frequencies coincide
- used in mobiles
- travel through air well
- smaller wavelength = more detail


infrared facts (8)

- emitted by all things colder than the temp. for emitting visible light
- all things give out radiation as infrared
- can make temp. map
- can be reflected
- can/can't pass through different things to visible light
- not good at passing through air
- goes past red on colour spectrum
- used in communication + thermal imaging


visible light facts (3)

- white light = combination of all frequencies
- when colour a is seen, all other colours are absorbed while a is reflected
- black = absence of light


ultraviolet light (3)

- can have harmful ionising effect
- fluorescent chemicals absorb uv light and emit it as visible light (eg washingup powder)
- uses: security marking, tooth whitening