P6-waves Flashcards
what two categories do all waves fall into
transverse and longitudinal
what are transverse waves and what do they do
-transverse waves (oscillations) are ripples on the water surface and transfer kinetic energy
-they move up and down
-these oscillations are perpendicular to the direction of energy transfer.
what are longitudinal waves and what do they do
-sound waves travel in air and transfer sound energy
-they travel as particles in the air and move side to side
-the oscillations are parallel to the direction of energy transfer
KEY POINT: they all require a medium to travel in; air, liquid or solid
properties of waves:
amplitude
wavelength
frequency
compression
rarefraction
-amplitude=the maximum displacement of a point from an undisturbed position
-wavelength=the distance from a point on one wave to the equivalent point on the adjacent wave.
-frequency=The number of waves passing a point each second. units= hz
-compression= particles are very close
-rarefraction= particles are spread out
what is wave speed
the speed at which the wave moves through the medium
what are electromagnetic waves
they are transverse waves that transfer waves from the source of the waves to an absorber.
eg. light
- can travel through a vacuum( in space) and at speed of 300,000,000m/s
electromagnetic spectrum
raw- radio waves
meat- microwaves
is- infrared
very- visible light
unsanitary- ultra violet
eXcept- x rays
giraffe- gamma rays
electromagnetic spectrum properties
r-low frequency long wavelength
m
i
v
u
eX
g-high frequency short wavelength
what is refraction of waves
Refraction can happen when any wave changes speed as it passes
from one medium to another.
-diagrams on google classroom slide 27-37
properties of waves 2
-lithium atoms give out a red light when heated
-emitting electromagnetic waves
how are electromagnetic waves produced in lithium
-When we heat atoms, we
cause electrons to move
from one energy level to a
higher one.
-When this electron returns to its
original energy level, it
generates an electromagnetic
wave (light).
what are hazards of electromagnetic waves
UV-increase the risk of skin cancer/ cause skin to age prematurely
xrays & gamma rays- ionising radiation which can cause mutations of genes/ increases risk of cancer
what does electromagnetic radiation damage depend on
type of radiation
dose of radiation (measured in sv or msv)
when are radio waves produced
they can be produced when electrons oscillate
(move backwards and forwards) in electrical circuits.
process of radio waves being produced
-radio waves can be
absorbed.
e.g. by an electrical circuit in an
aerial
-they now cause electrons in the circuit to oscillate.
-This can create an alternating
current with the same frequency as the radio waves.
uses of em waves:
radio waves
-Used to transmit radio and Terrestrial TV signals(received using an aerial )
-They can travel long distances before being absorbed
-Longer wavelength radio waves can also spread out between hills
-Can also reflect off a layer of charged particles in the atmosphere
-(the ionosphere) – This allows us to send radio waves very long
distances around the Earth
uses of em waves
micro waves
-Used for heating food (as most food contains lots of water
molecules which absorb the energy of microwaves which causes the temperature of the food to increase)
-Used to communicate with satellites in space as they can pass through the Earths atmosphere without being reflected or
refracted.
uses of em waves
infrared
-Emitted by electrical heaters and is also used to cook food in ovens.
-This is because the energy of infrared is easily absorbed by the
surface of objects.
-The infrared from the heater is absorbed by objects in the room;
making the room warmer.
-Used in infrared cameras e.g. to check heat loss in buildings.
uses of em waves
visible light
-Used in communication using fibre optics.
-Optical fibres are very thin strands of glass.
-We can transmit pulses of light down these fibres and use these
pulses to carry information.
-Optical fibres are used to carry telephone and cable TV signals
uses of em waves
x-rays & gamma rays
-Used for medical imaging.
-X-rays: used to visualise broken bones
-Gamma rays: used to detect cancers
-Both are very penetrative as they can easily pass through body tissue.
