Waves Flashcards
Write the definition of: Progressive Wave
Transfer of energy as the result of oscillations of the medium through which the energy is travelling
Write the definition of: Longitudinal Wave
The oscillation of particles is parallel to the direction of travel of the wave e.g. sound
Write the definition of: Transverse Wave
The oscillation of particles is perpendicular to the direction of travel of the wave e.g. waves on a string, electromagnetic
Write the definition of: Mechanical Waves
Energy is transferred through a medium (i.e. by the oscillations of particles)
Write the definition of: Amplitude
The maximum displacement from the equilibrium position
Write the definition of: Wavelength
The minimum distance between two points oscillating in phase, for example the distance between one peak to the next. The length of one complete wave cycle, in metres.
Write the definition of: Period
The time taken for one complete wavelength to pass a given point OR the time taken to complete one oscillation. Measured in seconds.
Write the definition of: Frequency
Write the definition of: Frequency
Write the definition of: Phase
The position of an oscillating particle or field at a given time on a wave cycle, expressed in degrees or radians, where 1 full wave cycle = 360 degrees or 2π radians.
how the intensity is related to the amplitude of a wave
intensity is proportional to amplitude squared
give the equation for intensity
power/area = intensity
Write the definition of: Intensity
The radiant power transferred per unit area (intensity = power / area). Measured in W m-2. Intensity is proportional to amplitude2
Write the definition of: Stationary Wave (Standing Wave)
A stationary wave is resultant of the superposition of two progressive waves of the same frequency, moving in opposite directions. The wave remains in a constant position and there is no net transfer of energy. The wave is characterised by its nodes and antinodes.
Write the definition of: Antinode
Point of maximum amplitude on a stationary wave
Write the definition of: node
Point of minimum amplitude on a stationary wave
Write the definition of: Fundamental Frequency
The lowest possible frequency at which a system can vibrate to create a standing/stationary wave
Write the definition of: Harmonic
A whole number multiple of the fundamental frequency
what is the difference between path and phase difference
they measure the same thing, but path difference measures it in terms of wavelength while phase difference is in radians and degrees
how can you find the frequency from an osciloscope trace
calculate the period by multiplying the t/div setting by the number of boxes equal to one wavelength. this gives you the period. then calculate the reciprocal of that value to get the frequency
how can you find the amplitude form an oscilloscope trace
the V/div setting times by the maximum number of boxes that one peak reaches
how can EM waves be produced
from varying electric and magentic fields
what is antiphase
when 2 points have a phase/path difference of pi, 190 degrees, or half a wavelength. when one is at a peak, the other is at a trough
give some wave properties
refract, reflect, diffract, diffuse
define a polarised wave
a transverse wave which only travels in one plane
how does polarisation work
a polariser is a matrerial which only lets waves through in one plane. these polarised waves can then only get through materials with the same polarisation or none at all
a polarising material in front of another is turned around 360 degrees, what observations could be seen
every 90 degrees the light intensity would reach a minimum or maximum in alternating order
a horizontal polariser is placed in front of a horizontal polariser, what will happen to the image through them and why
there will be no change because they both let through waves in the same direction. the image will remain at maximum intensity
a vertical polariser is placed in front of a horizontal polariser, what will happen to the image through them and why
the vertical poalriser polarises waves in the veritcal direction, so that there are non in the horixontal direction meaning that no waves will get through the horizontal polariser and the image will appear black
give two applications of polarisers and the reason for their use
in sunglasses because they do not allow some polarised llight through them, decreasing the light intensity that gets through to the eye
give the definition of destructive superposition
when 2 waves have aphase difference of 180 degrees, they superpose and the peaks cancel out thr trough
give the definition of constructive superposition
when 2 waves have a phase difference of 0 degrees and they superpose to form a waves that has the peaks and troughs as the sum of the previous waves’ peaks and troughs
give the deifniition of superposition
the process by which two propgressive waves travelling in opposite directions combin into a single wave form when they overlap
give the principle of superposition
the resultant displacement of waves is equal to the sum of individual displacements of the waves that are meeting
how do nodes and antinodes form
nodes form when destructive superposition occurs between 2 waves
and antinodes when constructive super position occurs
define a stationary wave
a waveform that is the sum of 2 progressive waves of opposite direction, and same amplitude and frequency
why do even numbered harmonics not exist for a pipe with one closed and one open ened
because by definition this type of pipe must have one node at one end and one antinode at the other, therefore its not possible for an even frequency to exist
what determines the number harmonic
the multiple of the fundamental fequency
in pipes, where do nodes and antinodes form
nodes form at closed ends, and antinodes form at open ends
what are coherent waves
waves with a constant phase difference
what is intensity
power over area
if you take the light emitted by a source to be a sphere, the intensity is the power per area a certain distance from the source.
what is the relationship between intensity and amplitude
I ∝ A²
define diffraction
The spreading of a wave after passing through a gap or around an obstacle
