wave Flashcards
what is amplitude
max displacement from equilibrium at a point
what is frequency
number of oscillations at a point per unit time
what is phase difference
how out of sync the oscillations are at two points
what is the main difference between a progressive and a stationary wave
progressive transfers energy; stationary stores energy
explain how a stationary wave is formed on a string
wave is reflected at fixed end of the string; reflection interferes with original wave; result is a wave with no energy transfer
how to find wavelength of standing wave
double the distance between two adjacent nodes
what is interference
resultant displacement = sum of individual displacements of two waves at a point
what does it mean when two waves are coherent
constant phase difference
relationship between intensity and amplitude
intensity proportional to amplitude squared
what are the conditions for a minimum in an interference pattern
constant phase difference of 180 degrees
what is intensity
power per unit area
what are two properties that are unique to EM waves
can travel through a vacuum; all travel at speed c in a vacuum
what is meant by a polarised wave
oscillations are in only one direction perpendicular to energy transfer
an object is put behind two perpendicular polarising filters; explain why it is not visible
filter 1: light is vertically polarised; filter 2: only horizontal light is let through; so no light gets to our eyes
an object is put behind three polarising filters, each at 0, 45, and 90 degrees; explain whether the object is visible
filter 1: light is vertically polarised; filter 2: vertical light is polarised to its 45 degree component; filter 3: 45 degree light is polarised to its horizontal component; so some light gets to our eyes
explain how a stationary wave pattern forms in a microwave oven
microwaves reflect off the walls; reflections interfere with original waves; standing wave pattern formed with nodes and antinodes, and no net energy transfer
what are the points of max amplitude in a standing wave
antinodes
what are the points of min amplitude in a standing wave
nodes
what is displacement
distance of a point from equilibrium
what are the wavelengths of all the EM waves
micro = 10^-4 m; infrared = 10^-6 m; ultraviolet = 10^-8 m; gamma = 10^-12 m
explain how minima and maxima occur in an interference pattern
constructive interference causing maxima where phase diff is 0; destructive interference causing minima where phase diff is 180
what is path difference
difference in distance travelled for two waves at a point
what is a transverse wave
wave with oscillations perpendicular to energy transfer
how to get more diffraction
make gap width equal to wavelength
why does amplitude of a circular wave decrease with distance
energy of the wave spreads out
what conditions are needed for an interference pattern between two sources
sources must be coherent; and have similar amplitude; and be close together so their waves overlap
what is resonance
when frequency of driving force equals natural frequency; this causes increased amplitude of oscillations
what is simple harmonic motion
acceleration is proportional to displacement; and acts towards equilibrium
