3.0 Waves Flashcards
What is a wave
The propagation of a quantity through the oscillation of a medium
Define amplitude
The maximum displacement a point on the wave oscillates from its equilibrium point
Define period
The time taken for one complete cycle of a wave
Define frequency
The number of cycles of the wave in a second
Define wavelength
The distance between two consecutive points in phase
Define phase
The position a point is along the cycle of a given wave
Define speed of a wave
The rate at which the wave passes through the medium
Define phase difference
The relative difference in phase between two points on a wave or two waves
What is phase difference measured in
As an angle in degrees or radians, or as a fraction of a cycle
Describe the nature of longitudinal waves
Direction of displacement parallel to direction of energy transfer
Describe the nature of transverse waves
Direction of displacement perpendicular to direction of energy transfer
Medium of longitudinal waves
Can propagate through any solid, liquid or gas
Medium of transverse waves
Can propagate through solids, some liquids and electromagnetic media
Examples of longitudinal waves
Sound waves and a horizontally oscillated slinky
Examples of transverse waves
Electromagnetic radiation, water waves and a vertically oscillated slinky
What speed do EM waves travel at in a vacuum
All have a speed of 3×10⁸
Define polarisation
The process where waves are restricted to oscillate in a specific direction or plane
Describe how polarisation provides evidence for the nature of transverse waves
Polarisation restricts oscillation in the perpendicular direction. Only transverse waves can be polarised. So transverse wave oscillate perpendicularly
Applications of polarisers
Polaroid material, optical fibers, photography, communication
What are stationary waves
Waves that oscillate but don’t pass through a medium
Energy transfer in stationary waves
Stationary waves transfer no energy from one point to another
Formation of a stationary wave
Formed from the superposition of two coplanar waves with equal wavelengths and magnitudes traveling opposing directions.
What is a node on a stationary wave
A point of minimum amplitude
Formation of a node
Waves are in constant antiphase, destructive interference occurs, resulting in point of minimum amplitude
What is an antinode on a stationary wave
A point of maximum amplitude
Formation of an antinode
constructive interference occurs, resulting in point of maximum amplitude
Formation of stationary waves on a string
Oscillator created wave on string which reflects at a fixed point. two waves superpose forming stationary wave
Define path difference
the difference in distances travelled by two waves
Define coherence
When two waves have the same frequency and have a fixed phase relationship
define monochromatic
When waves have the same wavelength
Sources of monochromatic light
Lasers, filters
Define diffraction
The process where waves light bends or spreads out when passing close to an object or through a slit in an object
Define interference
The process where two or more waves combine to form a single resultant wave
Youngs double slit experiment
The use of two coherent sources or the use of a single source with double slits to produce an interference pattern.
Problems with double slit formula
assumes small angle approximation so reduces accuracy
Describe an interference pattern
Equally spaced bright fringes separated by dark fringes, with reducing intensity from the center. Symmetrical on both sides
Describe an interference pattern with white light
central maxima of white light with outer fringes of spectrums, with red on the outside and green on the inside
what are some safety issues with lasers
Danger to eyes - wear goggles
Hard to notice - signpost
production of maximas in interference patterns
Waves are in phase so constructively interfere, creating a resultant wave of maximum amplitude
production of minimas in interference patterns
Wave are in antiphase so destructively interfere, creating a resultant wave of minimum amplitude
define constructive interference
When wave are in phase, they superpose and produce a wave of maximum amplitude
define destructive interference
When wave are in antiphase, they superpose and produce a wave of minimum amplitude
how has knowledge progressed
New experiments have allowed us to understand the nature of electromagnetic waves
Describe a diffraction pattern
Central maxima of double width with repeating dark minima and bright maxima of reducing intensity from center. Symmetrical on both sides
Describe a diffraction pattern with white light
A central maxima of white light with outer maxima being spectra, with red on the outside and green on the inside
Applications of diffraction gratings
spectrometry, fiber optics, telecommunications, astronomy
define refraction
The apparent bending of light when passing through a boundary from one medium to another
Refractive index of air
approximately 1
define total internal reflection
The complete reflection of light within a material above a certain angle of incidence
Parts of a fiber optic cable
core which is the medium that the light travels through and the cladding which protects the core and has a low refractive index, providing a low critical angle
define material dispersion
The broadening of a signal due to differences of speed for different wavelengths in the core
define modal dispersion
The broadening of a signal due to differing paths taken by different modes
Define pulse broadening
the spreading out of a signal due to dispersion, causing degradation of the signal
Define pulse absorption
the reduction of the signal due to absorption of energy in the atoms of the core
