Topic 4.4: Waves Flashcards
progressive wave
a wave which transfers energy from one place to another with a wave front which travels through a material
longitudinal wave
a wave which oscillate in the same direction as energy propagation
there are rarefactions and compressions
transverse wave
a wave where the particle oscillations are perpendicular to the energy propagation
what is frequency ?
the number of waves passing through a point per second
measured in Hertz
wavelength
the distance between two adjacent corresponding points on a wave
amplitude
the maximum displacement of the wave from its equilibrium position
what is the phase difference ?
the amount one wave lags behind another as a proportion of the wavelength
measured in radians or degrees
refraction
is when a wave bends at a boundary between two materials due to the difference in density causing it to speed up or slow down
what is the difference between polarised and unpolarised waves ?
polarised waves only contains waves oscillating on one axis
unpolarised waves can be oscillating in any direction perpendicular to the axis propagation
describe how a ripple tank may be used to investigate diffraction
create water waves in the tank
vary the size of a gap for them to pass through
note how the direction of the waves passing through changes
How is intensity defined in terms of power ?
intensity is power/area
how are intensity and amplitude related
intensity is proportional the amplitude squared
what is the refractive index of a material ?
it is a measure of how fast light travels in a material compared to its speed in a vacuum
n = c/v speed of light / velocity in material
what is superposition ?
what are coherent waves ?
coherent waves have the same frequency and wavelength and a fixed phase difference
what is path difference ?
path difference is the difference that two waves have travelled in terms of wavelength
what is phase difference ?
phase difference is the difference in the point in the cycle of two waves as a proportion of a full wave cycle
why is a laser useful in showing interference and diffraction ?
it produces monochromatic (same wavelength/colour)
what is Youngs double slit experiment ?
a single source of light directed towards a double slit , which creates two coherent beams of light.
this interferes as it hits the screen and creates an interference pattern
what two properties can only be explained if it is a wave ?
diffraction
inteference
what is a stationary wave ?
stationary waves consists of alternating fixed pattern of nodes (points with zero amplitude) and antinodes (points with maximum amplitude)
no energy is transferred across the wave
what is a node ?
a point with no vibrations in which the resultant amplitude is 0
what is an antinode ?
a point with maximum vibration in which the resultant amplitude is at maximum
what are the conditions for a stationary wave to be produced ?
the waves must be coherent
they must be travelling in opposite directions
