general waves Flashcards
what do waves do
transfer energy without transferring matter
what is frequency
number of wavelengths passing a given point per unit time
what is a wave period
the time for one oscillation
define wavelength
the distance between identical points with the same phase
what is the phase of a wave
describes how far through a cycle the wave is.
what is the phase difference
phase difference measures the difference between where two waves are in the cycle. it can be measured as an angle or a fraction of the wavelength
what is a transverse wave
the particles oscillate perpendicular to the direction of energy transfer
what is a longitudinal wave
the particles oscillate parallel to the direction of energy transfer
electromagnetic waves information
all are transverse,
all travel 3*10^8 m/s in a vacuum,
electric+magnetic fields oscillate perpendicular to the energy propagation
define amplitude
the maximum displacement from the equilibrium position
what is polarisation
when the oscillation of a wave is restricted to one plane. must be a transverse wave. oscillations must be perpendicular to the direction of energy transfer
what is a polariser
a material that limits the plane of oscillation
how does a polaroid material work
the molecules form parallel lines uniformly spaced
Any polarisation direction that is parallel to the molecules is absorbed,
Any polarisation direction that is perpendicular to the molecules is transmitted,
The transmitted light is at a lower intensity
what happens to unpolarised light when reflected
when reflected from a transparent surface light becomes partially polarised parallel to the surface
what would happen if two polarisers were placed next to each other with a 90° difference in orientation
no light could get through. the first one only transmits horizontally polarised light and the second would be vertically polarised only. so no light could get through both. (or the other way around)
how are television/radio aerials oriented
they can be oriented so the spokes are horizontal or vertical. if a transmitter is sending out vertically polarised waves then the spokes should be vertical for maximum absorption of the waves for a good signal.
how is a stationary wave formed
when two progressive coherent waves are moving in opposite directions and interfere with each other.
what is a node
points on a standing wave of destructive interference
whats an antinode
points on a standing wave of constructive interference
whats a resonant frequency
frequencies that can form stationary waves.
what are harmonics
resonant frequencies. they can form stationary waves. they are integer multiple of 1/2λ plus the fundamental frequency
relationship between string length and frequency
long string length causes smaller frequency. because longer length causes a longer half-wavelength so there’s a lower frequency
relationship between mass per unit length and frequency
greater mass per unit length = smaller frequency. because waves travel slower through a heavier string so the frequency will be lower if the string is a constant length
relationship between tension and frequency
higher tension = higher frequency. because waves travel more quickly through a string with higher tension
why does the soundhole in a guitar increase the pitch
The soundhole allows more air to be adjacent to the string while forming a resonant cavity which amplifies the sound waves
what two properties of a wave are directly proportional
amplitude^2 and intensity
define progressive wave
waves that transfer energy from one place to another but do not transfer matter
define wave speed
the distance travelled by a wave per unit time
define intensity
the power passing through a surface per unit area
range of wavelengths of visible light
450-700nm
why can x-rays and gamma rays have an overlap in there possible wavelengths
EM waves are defined by there sources not there wavelengths
