Waves and Seismic waves Flashcards
What are the 2 types of waves
Longitudional and Transverse
Amplitude
Maximum displacement from equilibrium
Wavelength
length of one complete wave cycle - distance from peak to peak or compression to compression
Frequency
Number of oscillations or cycles per second
Time period
Amount of time it takes for wave to occur
Transverse wave
A transverse wave is a wave that oscillates perpendicular to its propagation. A wave that vibrates at right angles to the direction of energy transfer.
Longitudional wave
In longitudinal waves, the vibrations are parallel to the direction of wave travel. Longitudinal waves show areas of compression and rarefaction:
Compression
compressions are regions of high pressure due to particles being close together
Rarefraction
rarefactions are regions of low pressure due to particles being spread further apart
example of longitudional wave
stretched spring
example of transverse waves
ripple in water surface
frequency =
measured in Hertz
1 / time period
wavespeed =
frequency x wavelength
OR
distance / time
What do sound waves cause in solids
vibrations as sound travels through solids
what type of waves are sound waves
longitudional
Waves cannot be reflected at the boundary between 2 different materials : True or False
False : they can
Waves can be absorved or transmitted at the boundary between 2 different materials : True or False
True
what causes sound
vibrations
Mechanical Waves
needs a medium to pass through
Medium
A general name for a material that a wave is passing through.
reflection
This occurs when a wave travelling in one medium strikes the surface of a different medium and changes direction so that it returns back into the medium in which it was originally travelling in.
Transmission
Transmission is the movement of a wave through a medium or from one medium into another.
Absorption
Absorption is when the energy being transferred by a wave is taken into an energy store of a material.
Can sound waves can travel through solids causing vibrations in the solid?
yes
how do we feel the sensation of sound
Sound waves make ear drum vibrate, causing sound. Conversion of sound waves to vibrations of solids works over a limited frequency range.
frequency range of normal Human hearing
20 Hz to 20kHz
Ultrasound
Waves with a frequency higher than the upper hearing limit for humans
what happens when ultrasound waves meet the boundary of 2 different media
they are partially reflected
How can ultrasound waves be used for medical and industrial imagery.
Time taken for reflections to reach detector can be used to determine the distance to the boundary when the speed of the wave is known.
Speed of sound in air?
330 m/s
what is a reflected sound called
echo
are hard or soft surfaces best at reflecting sound
hard surfaces
Focus
The focus is the place inside Earth’s crust where an earthquake originates
Epicentre
The point on the Earth’s surface directly above the focus is the epicentre
what two waves do earthquakes produce
Shock waves and seismic waves
two types of seismic waves
P waves and S waves
What are P waves
longitudional seismic waves, travels fastest and through solids, liquids or gases.
why do P waves travel fastest in solids
p-wave velocity increases with depth and increases with increasing rigidity of a material.
S waves
transverse seismic waves, can only travel through solid. Slower than P waves
Law of reflection
angle of incidence = angle of reflection
Angle of incidence
The angle of incidence is the angle between the direction of motion of the wave and a line drawn perpendicular to the reflecting boundary.
how are angle of incidence and reflection measured
The angles of incidence and reflection are measured between the light ray and the normal - an imaginary line at 90° to the surface.
Specular reflection
Reflection from a smooth, flat surface is called specular reflection. This is the type of reflection that happens with a flat mirror.
Diffuse reflection
If a surface is rough, diffuse reflection happens. Instead of forming an image, the reflected light is scattered in all directions. This may cause a distorted image of the object, as occurs with rippling water, or no image at all. Each individual reflection still obeys the law of reflection, but the different parts of the rough surface are at different angles.
