p6 waves Flashcards
what do waves transfer?
waves transfer energy in the direction that they are travelling in
what is a medium?
a medium is a substance at which a wave a propagate
what happens when a wave travels through a medium?
the particles of the medium oscillate and transfer energy between eachother. but overall, the particles stay in the same place, only energy is transferred
what is the amplitude of a wave?
the maximum displacement of a point on a wave from it’s undisturbed position
what is the wavelength of a wave?
the distance between the same point on two adjacent waves
what is the frequency of a wave? and what is it measured in?
the number of complete waves passing a certain point per second, it is measured in hertz. one Hz is 1 wave per second
what is the period of a wave?
the amount of time it takes for a full cycle of the wave to pass a point
what is the distinguishing property of traverse waves?
their oscillations are perpendicular to the direction of the energy transfer. for example, a spring wiggling from side-to-side
what are some examples of traverse waves?
1) electromagnetic waves, eg light
2) ripples and waves in water
3) a wave on a string
what is the distinguishing property of longitudinal waves?
the oscillations are parallel to the direction of energy transfer. for example, pushing the end of a spring gets you a longitudinal wave
what are some examples of longitudinal waves?
1) sound waves in the air, eg ultrasound
2) shock waves, eg some seismic waves
what types of waves are all EM waves?
they are all traverse waves, which transfer energy from a source to an absorber. for example, a hot object transfers energy by emitting infrared radiation, which is absorbed by the air
do all EM waves travel at the same speed through air or a vacuum?
yes
what do EM waves form and how are they grouped?
1) they form a continuous spectrum over a range of frequencies.
2) they’re grouped into 7 basic types based on their wavelength and frequency
what are the 7 parts of the electromagnetic spectrum?
LISTED FROM INCREASING FREQUENCY AND DECREASING WAVELENGTH:
1) radio waves
2) microwaves
3) infrared
4) visible light
5) ultraviolet
6) x-rays
7) gamma rays
why is there such a range of frequencies of EM waves?
because EM waves are generated by a variety of changes in atoms and their nuclei - this also can explain why they can absorb different frequencies, cause each one causes a different change
what are EM waves made up of?
oscillating electric and magnetic fields
what are radio waves made by?
oscillating charges
how can you create radio waves?
1) the frequency of the EM waves produced by oscillating current will be equal to the freq of the alternating current.
2) to produce radio waves, you can use the alternating current in an electrical circuit.
3) the object in which electrons oscillate to create radio waves called a transmitter.
4) when transmitted, radio waves reach a receiver, where they are absorbed.
5) the energy transferred by the waves is transferred to the electrons in the material of the receiver. where they then cause the electrons to oscillate, and if the receiver is part of a complete circuit, it generates an AC.
6) this current has the same freq as the radio waves that generated it.
what are radio waves used for?
mainly for communications
how are long-radio waves good for their use?
they can be transmitted and received from halfway around the world.
- this is because they diffract around the surface of the curved earth.
- they can also diffract around hills and into tunnels ect
therefore this makes it possible for radio waves to be received, even if it isnt in the line of the transmitter
how are short-radio waves good for their use?
they can be received at long distances from the transmitter.
- this is because they are reflected from the ionosphere- an electrically charged layer on the Earth’s upper atmosphere
what uses short- radio waves?
bluetooth uses short-radio waves to send data over short distances between devices without wires
why are medium waves good for their use?
can reflect from the ionosphere, depending on the atmospheric conditions and the time of day