EX unit three: waves Flashcards
what types can waves be divided into?
mechanical waves and electromagnetic waves
mechanical waves
waves that need a material medium to travel through
electromagnetic waves
waves that can travel through a vacuum
what can waves transfer?
energy and information without transfer of matter
what types can mechanical waves be divided into?
transverse and longitudinal waves
transverse waves
the oscillations of the spring are perpendicular to the direction of energy transfer along the spring
longitudinal waves
the oscillations of the spring are parallel to the direction of energy transfer along the spring
when a wave travels above its rest position on a diagram is it positive or negative displacement?
positive
when a wave travels below its rest position on a diagram is it positive or negative displacement?
negative
define wavelength
the distance between corresponding points in the wave - one crest to the next crest in a transverse wave.
define amplitude
the maximum movement of particles from their resting or equilbrium position
what are wavefronts
a line where all the vibrations are in phase and the same distance from the source
what is the period of a wave
the time for one complete cycle of the wave, from wavelength to wavelength.
what is the frequency of the wave
the number of cycles the waves form per second
what is frequency measured in (provided the frequency is in seconds)
hertz (Hz)
frequency =
1 / period
wave speed =
frequency x wavelength
what is the symbol for wavespeed
v
what is the symbol for frequency
f
what is the symbol for wavelength
lamda λ
what is wavelength measured in
m
what is wave speed measured in
m/s
what is a ripple tank
a simple piece of apparatus that makes it possible to show how waves behave.
describe the movement of waves in a stationary vehicle’s engine. how does this affect the sound?
the soundwaves arrive as a series of equally spaced wavefronts. people in front or behind the vehicle hear a sound of the same frequency and wavelength.
describe the movement of waves in a moving vehicle’s engine. how does this affect the sound?
the soundwaves are no longer evenly spaced wavefronts, they will be compressed and have a shorter wavelength. this means they will have a higher frequency and the person hears a higher pitch. behind the car the soundwaves are spaced out and have a longer wavelength. this means they will have a lower frequency
what is the order of the electromagnetic spectrum
radio waves - microwaves - infrared - visible light - ultraviolet - xrays - gamma rays
does frequency increase or decrease along the electromagnetic spectrum
increase
does wavelength increase or decrease along the electromagnetic spectrum
decrease
what is the order of colours in the visible part of the electromagnetic spectrum?
red - orange - yellow - green - blue - indigo - violet
what are electromagnetic waves
transverse changes in the electric and magnetic fields in space.
uses of radiowaves
communication of information e.g. speech, radio, tv
what waves have the lowest frequencies and the longest wavelength
radio waves
uses of microwaves
heating food and satellite communciation.
uses of infrared
night vision cameras and heating devices.
uses of visible light
used by humans to see things and photography.
uses of ultraviolet
black lights and sterilising water
uses of x-rays
used to examine the internal structures of the body in medical diagnosis.
uses of gamma rays
sterilising medical equipment and treating cancer.
dangers of microwaves
they can directly heat internal body tissue
dangers of infrared
its readily absorbed by our skin and will cause burns