waves- topic 3 Flashcards
waves
Oscillations in a medium that transfer energy not matter
wave motion
Wave motion is the transfer of energy from one point to another. We can demonstrate this by hanging an object on a stretched string and then sending a pulse down the string (by moving it up and down quickly like a wave)
oscillation
vibration repeated side to side or back and forth motion in a fixed point
displacement
distance from rest position (0 displacement)
amplitude (A)
a wave is its maximum distance from the equilibrium.
maximum displacement
from x axis to wave peak (A)
wavelength
distance between successive crests or successive troughs
crest (peaks) vs troughs
crests=The peak of a wave. The part of a wave at maximum amplitude.
troughs=The bottom of a wave. The point with minimum amplitude.
frequency
the number of waves produced each second. It is denoted by the letter f and is measured in hertz (Hz).
wavefront
an imaginary surface that we draw to represent the vibrating part of a wave
wave speed
the distance travelled by a wave each second.
frequency * wavelength
transverse waves
the particle oscillates perpendicular (at right angles) to the direction of propagation of the wave
electromagnetic radiation, water waves and
seismic S-waves
troughs and crests
longitudinal waves
the oscillation of the particles is parallel (in the same direction) to the direction of propagation of the wave
sound waves
and seismic P-waves (primary)
rarefactions and compressions
reflection of a wave
a wave ‘bounces’ off a boundary
changes direction
wave speed, frequency and wavelength does not change
rarefraction of a wave
a wave moves from one medium to another
change in speed caused by movmeent form one material to the other causes a change in wavelength, can also cause change in direction in which wave is travelling depending on angle wavefront reaches boundary
If the wavefronts are parallel to the boundary, the wave will just change speed
no change in direction
diffraction
a wave spreads as it moves through a gap. curved pattern
incident ray
The path of a wave which travels from the source. reaches boundary
reflected wave
The path of a wave which has reflected from a surface. hit boundary and bounced off
what happens if wavefront is parallel to surface when it hits
wavefront will be reflected back in the direction it came from
what happens when waves travel from deep to shallow if not parallel to block
waves slow down, due to this frequency does not change, and wavelength decreases
direction of travel will change towards the normal. angle of rarefaction is smaller than incidence wave
what are two ways to increase diffraction
decrease size of the gap
increase wavelength of wave
A gap width similar to the wavelength of the waves passing through causes a lot of spreading
Describe how wavelength affects diffraction at an
edge
this amount of diffraction increases as the wavelength of the wave increases. Waves with long wavelengths diffract more than waves with short wavelengths.
what diffracts more and why? sound or light waves through an edge
As sound waves have much longer wavelength than light waves they are much more strongly diffracted by edges. This allows sound waves to spread around corners in a way that is not possible for light.
describe refraction from deep water to shallow water at an angle
wave travelling through deep water is faster, when it enters shallow surface, it slows down and this causes a change i direciton, when waves slow down wavelengths decrease, angle of incidence is bigger than angle of rearefraction, getts smaller with bigger angle
what happens when a wave is travlleing from deep water to shallow water but is parallel to boundary
no change in direction only change in speed goes from fast to slow, wavelengths decrease