waves Flashcards
what are the two types of waves
transverse and longitudinal
what do waves transfer?
they transfer energy from one place to another
what’s an example of transverse waves
ripples on water surface (transfer kinetic energy)
what’s an example of longitudinal waves
sound in air (transfer sound energy)
what do longitudinal waves require
medium to travel in
what do not all transverse waves require
medium
define amplitude
furthest point from undisturbed position
define wavelength
distance between indentical points of a wave
define frequency
the number of waves produced in a second
what’s the period equation
period (s) = 1/ frequency (Hz)
what’s the frequency rule
1 second = 1 Hertz Hz
what’s the wave equation
wave speed (m/s) = frequency (Hz) x wavelength (m)
define wave speed
speed at which energy is transferred
what’s an example of an EM wave
light
all EM waves are …
transverse
define EM waves
they transfer energy from the source of the wave to an absorber
explain how a microwave is an EM wave
transfers energy from the oven (source) to the food (absorber)
what is the EM spectrum
radio
microwave
infrared
visible light
ultraviolet
x-ray
gamma rays
at the start of the spectrum the properties of the waves are….
lower frequency and longer wavelength
at the end of the spectrum the properties of the wave are ….
higher frequency and shorter wavelength
what is the pneumonic for EM spectrum
Raw Meat Is Very Unsanitary eXcept Giraffes
do EM waves need a medium to travel in?
No because they are transverse
what else can EM waves travel?
vacuum
do EM waves vary speeds in a vacuum
no they all travel in the same speed
what speed to EM waves travel in a vacuum
3 x 10 to the power of 8 m/s
different materials ….. …… or …….. EM waves
absorb transmit or reflect
waves change direction when they change ……
speed
when do EM waves change speed
moving from one medium to another
when light passes from air to glass …….
the velocity of light decreases (light wave slows down) which causes direction of wave to change
when the wave passes from the glass back to the air …
the velocity increases (speeds up) then they bond away from the normal
what material allows the most IR emission
matt black (leslie cube)
what material let’s the least IR radiation occur
shiny metallic
which surfaces absorbs more infrared
matt black
which surfaces absorbs less infrared
shiny metallic
when EM waves are generated or absorbed what happens to atoms or nuclei
changes happen
when atoms are heated what happens
electrons move from one energy level to a higher one (further from the nucleus)
what happens when an electron returns to its original energy level
it generates an EM wave
what ray can be emitted by the nucleus
gamma rays
once emitted out of a radioactive atom what happens to the nucleus
it has less energy that at the start
what waves are hazardous to the human body
UV, x-ray and gamma
what can UV cause to humans
skin cancer and premature aging
what do x-ray and gamma rays do to the human body
they are ionising radiation so they can cause mutation of genes (increase of cancer risk)
what are radio waves used for
transmit radio and terrestrial TV signals
give one example why radio waves used for what they are used for
they travel long distances
what are microwaves used for
heating food
communicate with satellites in space
give one example why microwaves used for what they are used for
can pass through earth’s atmosphere without being reflected or refracted
what is infrared used for
emitted by electrical heaters
cook food in ovens
infrared cameras
give one example why infrared is used for what they are used for
easily absorbed by surface of objects
what is visible light used for
communication using optic fibres (telephone and cable TV signals)
what is ultraviolet used for
energy efficient light bulbs
sun tanning (sun beds)
give one example why UV is used for what they are used for
less energy needed and used
what can we use x-rays and gamma rays for
medical imaging
x-ray - broken bones
gamma - detect cancer
medical treatment- treat cancer
give one example why x-rays and gamma rays are used for what they are used for
very penetrating
x-rays are absorbed by bones
what is the speed of sound in air
330 m/s
