# Physics P6 (Waves)

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What are the different types of waves?
transverse and longitudinal
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What is a transverse wave?
A wave that vibrates at right angles to the direction of energy transfer
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What is a longitudinal wave?
A wave that vibrates parallel to the direction of energy transfer
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Example of a transverse wave?
The ripples on a water surface
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what do longitudinal waves show areas of?
compression and rarefaction
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Example of a longitudinal wave?
sound waves travelling through air
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define amplitude of a wave
the maximum displacement of a point on a wave away from its undisturbed position.
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define wavelength of a wave
the distance from a point on one wave to the equivalent point on the adjacent wave
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define frequency of a wave
the number of waves passing a point each second
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How can you work out the period of a wave?
1/frequency
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What is the unit for frequency?
hertz (Hz)
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What is the unit for period?
seconds (s)
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define wave speed?
the speed at which the energy is transferred (or the wave moves0 through the medium
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how can you work out wave speed?
frequency x wavelength
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what 3 things waves do at a boundary between two different materials?
reflected, absorbed, transmitted
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what do sound waves cause in the solid when they travel through solids?
vibrations
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what causes the sensation of sound?
sound waves that cause the ear drum and other parts to vibrate
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what does this conversion of sound waves to solids work over?
a limited frequency range
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what does this restrict?
the limits of human hearing
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what si the range of normal human hearing?
20Hz-20kHz
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in terms of human hearing, what does ultrasound waves have?
a frequency higher than the upper limit of human hearing
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to what extent are ultrasound wabes reflected when they meet a boundary between two different media?
partially reflected
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what is calculated to determine how far away a boundary is?
the time taken for the reflections to reach a detector
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what does this allow ultrasound waves to be used for? (2 things)
medical and industrial imaging
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what waves are produced by earthquakes?
seismic waves
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what are P-waves?
longitudinal, seismic waves
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what can P-waves travel through and are the speeds the same?
they travel through solids and liquids at different speeds
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what are S-waves?
transverse, seismic waves
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Whst can S-waves travel through?
solids, not liquids
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what can P and S waves provide evidence for?
the structure and size of the Earth's core
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what did the study of seismic waves provide in terms of parts of the Earth?
new evidence that led to discoveries about parts of Earth which aren't directly observable
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What type of waves are electromagnetic waves?
transverse
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what do electromagnetic waves do?
they transfer energy from the source of the waves to an absorber
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what is the velocity like with all electromagnetic waves?
the same through a vacuum (space) or air
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how are electromagnetic waves in the electromagnetic spectrum grouped in terms of?
their wavelength and frequency
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what is the order of the electromagnetic waves from left to right?
radio, microwave, infrared, visible light, ultraviolet, X-rays and gamma rays
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what colours make up visible light?
red, orange, yellow, green, blue, indigo, violet
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is going left to right increasing what?
frequency
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is going right to left increasing what?
wavelength
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why do we detect a limited range of electromagnetic waves?
our eyes detect only visible light
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what may different substances do to electromagnetic waves in ways that vary with wavelength?
absorb, transmit, refract or reflect
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why does refraction happen?
due to the difference in velocity of the waves in different substances
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what can radio waves be produced by?
oscillations in electrical circuits
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what may be created when radio waves are absorbed?
an alternating current with the same frequency as the radio wave itself
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what does this the allow radio waves to do?
induce oscillations in an electrical circuit
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what can the changes in atoms and nuclei of atoms result in?
electromagnetic waves being generated or absorbed over a wide frequency range
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what do gamma rays originate from?
changes in the nucleus of an atom
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what 3 electromagnetic waves can have hazardous effects on human body tissue?
ultraviolet, X-rays and gamma rays
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What two things do the effects depend on?
type of radiation and the size of the dose
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what is radiation dose (sieverts),a measure of?
the risk of harm resulting form an exposure of the body to radiation
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what can UV waves cause skin to do?
age prematurely
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what can this increase the risk of?
skin cancer
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what 2 electromagnetic waves are ionising radiation?
X-rays and gamma rays
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what can these waves cause?
the mutation of genes and cancer
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What are the 2 uses of radio waves?
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What are the 2 uses of microwaves?
satellite communications, cooking food
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What are the 3 uses of infrared?
electrical heaters, cooking food, infrared cameras
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What is the 1 use of visible light?
fibre optic communications
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What are the 2 uses of ultraviolet?
energy efficient lamps, sun tanning
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What are the 2 uses of X-rays and gamma rays?
medical imaging and treatments
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How does a lens form an image?
by refracting light
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in a convex lens, where are parallel rays of light brought to a focus?
at the principal focus
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what is the focal length?
the distance from the lens to the principal focus
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what are ray diagrams used to sow the formation of? (2 types)
convex and concave lenses
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what is the image produced by a convex lens?
either real or virtual
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what is the image produced by a concave lens?
always virtual
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are images made from concave lenses always in front or behind the mirror?
behind the mirror
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how can the magnification produced by a lens be calculated?
image height/object height
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what are the units for magnification?
is a ratio so has no units
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what should image height and object height be measured in?
either mm or cm (for both)
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what does each colour within the visible light spectrum has its own narrow band of?
wavelength and frequency
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what is specular reflection?
reflection from a smooth surface in a single direction
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what does reflection from a rough surface cause?
scattering
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what is this called?
diffuse reflection
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how do colour filters work by?
by absorbing certain wavelengths (and colour) and transmitting other wavelengths (and colour).
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what is the colour of an opaque object determined by?
which wavelengths of light are more strongly reflected
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what happens to wavelengths that are not reflected?
they are absorbed
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when do objects appear white?
when all wavelengths are reflected equally
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when do objects appear black?
when all wavelengths are absorbed
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what are objects that transmit light either?
transparent or translucent
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what do all bodies (objects) , no matter what temp, emit and absorb?
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what happens if the body is hotter?
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what is a perfect black body?
an object that absorbs all of the radiation incident on it
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what does a black body not do?
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what is a good absorber also?
a good emiitter
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so what would a perfect black body also be?
the best possible emitter
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what do all bodies do?
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what does the intensity and wavelength distribution of any emission depend on?
the temperature of the body
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what is a body at constant temp doing?
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when does a temp of a body increase?
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what are some factors that the temp of earth depend on?
rates of absorption and emission of radiation, reflection of radiation into space
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## Other cards in this set

### Card 2

#### Front

What is a transverse wave?

#### Back

A wave that vibrates at right angles to the direction of energy transfer

### Card 3

#### Front

What is a longitudinal wave?

### Card 4

#### Front

Example of a transverse wave?

### Card 5

#### Front

what do longitudinal waves show areas of?