Waves Flashcards
What is the EM spectrum?
The full range of frequencies of EM waves, from gamma rays to radio waves
Define amplitude
The maximum displacement from the equilibrium position
Define frequency
The number of wavelengths passing a given point per unit time
What is the wave equation?
Wavespeed = wavelength x frequency
Define wave intensity
The radiant power passing through a surface per unit area
Define reflection
The change of direction of a wave at a boundary between two different media, so that the wave remains in the original medium
n(refractive index) =
c(speed of light in a vacuum)/v(speed of light in a material)
The critical angle is:
The angle at which light is refracted at 90 degrees
What is TIR?
When all of the incident light is reflected at a boundary going into a medium of lower refractive index
Diffraction is:
The phenomenon in which waves passing through a gap or around an obstacle spread out
Polarisation is:
The phenomenon in which oscillations of a transverse wave are limited to only one plane
Polarisation can only occur in
Transverse waves
Uses of polarisation include
Ariel
Stress analysis
Polaroid filters
The principle of superposition states
When two similar types of wave meet at a point the resultant displacement at that point is equal to the sum of the displacement of the individual waves
What is interference?
The superposition of two progressive waves from coherent sources to produce a resultant wave with a displacement equal to the sum of the individual displacements from the two waves
Phase difference is
The difference between the displacements of particles along a wave, measured in degrees or radians, with each complete cycle represented 360 degrees or 2pi radians
Coherence is
Two wave sources, or waves, that have a constant phase difference
Destructive interference is
Superposition of two waves in antiphase so that the waves cancel each other out and the resultant wave has a smaller amplitude than the original wave
Constructive interference
Is superposition of two waves in phase so that the resultant wave has a greater amplitude
Path difference
Is the difference in the distance travelled by two waves from their source to a specific point
Powers of typical wavelengths of em spectrum
Radio - 3 micro - -2 infrared - -5 visible - 7 x 10^-7 - 4 x 10^-7 ultra violet - -7 x rays - -9 gamma rays - -14
What is difference between the amplitude of a progressive and stationary wave?
progressive - All parts of the wave have the same amplitude ( assuming no energy losses)
Stationary - Maximum amplitude occurs at the antinode and then drops to zero at the node
In a stationary wave all parts of the wave between two nodes are …
in phase
In a stationary wave all parts of the wave on either side of a node are …
in anti phase
What is a harmonic?
An integer multiple of the fundamental frequency
