Waves Flashcards
define electromagnetic waves
oscillations, electrical or magnetic fields, through spaces (no material needed)
eg. electromagnetic spectrum
define mechanical waves
waves that pass through a material and vibrates the material
eg. sound waves, seismic waves, strings
define transverse waves
oscillations perpendicular to the direction of travel
define longitudinal waves
occurs when the medium moves parallel to the direction of the travel
labels on a longitudinal wave diagram
compression, rarefaction
labels on a transverse wave diagram
wavelength, amplitude, crest, trough, velocity of propagation
define time period
time taken for one wavelength to pass a point (s)
define frequency
number of wavelengths passing the same point per second (Hz)
define oscillation
back and fourth motions about a midpoint
define wavelength
distance between 2 identical point on a wave (m)
define amplitude
maximum displacement of a wave from the midpoint to the top of the crest
define wave
method of transferring energy from one place to another without transferring matter
define medium
matter a wave travels through
define wave propagation
any of the ways a wave travels
most ____ need mediums to exist
waves
_______________ waves may occur in a vacuum + material _______
electromagnetic, medium
_______ mostly depends on _______ of the medium
velocity, density
wave equation
v=fλ ms−1 = Hz x m
define rarefaction waves
change in direction of waves as they pass from one ,medium to another
rarefaction index equation
n=sin i/sin r
define reflection
occurs when light traveling through one material bounces off a different material
Define principle superposition
Whenever 2 waves are travelling in the same region the total displacement to any point is equal to the very tor sim of their displacements at any point
Waves either add together (constructive) on cancel out (destructive)
Define wave interference phenomenon
2 waves meet while travelling along same medium
What coherence measures
Ability of waves to interfere with eachother
Constructive produces bright light
Destructive isn’t coherent does produce light
Phase difference
If waves start at same point what is phase difference
No phase difference
Wavelength depends on
Amount of diffraction
The longer the wavelength the longer the diffraction
Wave types in EM spectrum
Gamma X-ray ultraviolet visible light infrared microwave radio
Speed of in em wave
3 x 10^8 ms-1
What type of waves are em waves
Transverse
How many groups of em waves
2
What waves are in group 1
Gamma uv X-ray
What waves are in group 2
Microwaves Infared visible
Effects of group one
Heating and ionising
Effects of group 2
Heating
What is ionisation caused by
High frequency electromagnetic radiation that delivers large amounts of energy if it’s absorbed.
What happens when em radiation ionoises an atom
The atom loses an electron and becomes and ion (positive charged particle)
These ions aren’t very reactive and can cause chemical reactions to occur that might lead to the damage of cell DNA that can cause mutations to occur
Define coherence
A fixed relationship between the phase difference of waves
Define refraction
A change in direction of a wave as it passes from one medium to another
What is excitation
Electrons absorbs energy and move to a higher energy level
What is de-excite
Gives out energy (light) goes down an energy level
Photon = radiation
Energy of emitted photon is
The difference between energy levels
hf = energy of photon emitted
hf = change in e
f = change in e / h
H = planks constant
Define path difference
The difference in the distance travelled by two coherent waves to the same point
Define diffraction grating
A screen with many slits close together
How are bright spots formed by diffraction grating
Typical pattern produced by light passing though a diffraction grating shows maximum surrounded by minima and bright fringes in an alternating pattern
How is emission spectra formed
By heating material causing electrons to jump to higher energy levels and then give off light as they fall back to a lower energy level
What is Absorption spectrum
When passing light through a gas wavelengths will be absorbed as electrons gain energy causing certain wavelengths to be missing from the spectrum of light
Define progressive wave
A wave that transfers energy from place to place
Define stationary wave
A wave that stores energy instead of transferring it
What is a node
A point on a stationary wave with zero displacement
Define Resonance
When a stationary wave is produced in an object
Define Natural frequency
The frequency which an form a stationary wave in an object
Define driving force
An oscillation force that causes a resonance
Define tension
The force pulling a string tight
Why is communication satellite
An object that sits in an orbit above earth, relaying communication signals
What is wifi
A wireless internet signal from a router connected to optical fibres
What is Bluetooth
A signal connecting two selected devices over a short distance using signals or a similar frequency to wifi
What is radio waves used for
Radio tv broadcast mobile phones
What is infared waves used for
Cooking food, remote controls, thermal cameras
What is visible light waves used for
Sight, illumination, cameras
What is microwaves used for
Cooking food , radar
What is ultraviolet waves used for
Tanning, blacklights
What is X-ray waves used for
Medical imaging
What is gamma rays waves used for
Medical imaging, radiotherapy, sterilisation
How commas satellites works
Sits in orbit above earth
Microwaves are transmitted to satellites
Waves are retransmitted to earth
Allows microwaves ti he transited around curve of earth
How phones communicate
Radio waves or microwaves frequencies transmit data
Signal sent to antenna
Antenna sends signal through a network to another antenna
Higher frequency signal aves transmit data quicker
How Bluetooth and wifi work
Highly frequency radio waves transmit over short distances
Wifi continuously transmits Bluetooth is short distances
