P12 Wave Properties Flashcards
What are the differences between P waves and S waves?
- P waves are longitudinal and can travel in liquids and
solids - S waves are transverse and cannot travel in liquids
Name 3 types of seismic waves
P waves
S waves
Surface Waves (Longitudinal)
What medium do P waves travel faster in?
They travel in solids faster than liquids
What is the “S wave shadow”?
A place where only P waves are received, as the S waves cannot travel through the liquid outer core
What are the 4 layers of the Earth?
Crust (solid earth and rock)
Mantle (solid)
Outer core (liquid iron and nickel)
Inner core (solid iron and nickel)
Why is the inner core a solid despite being hotter than the outer core?
There is a greater pressure on it
Why do P and S waves change direction gradually inside the earth?
As there is a gradual change in density, causing the waves to refract, changing their speed, and therefore their direction
Where does the largest change in direction of a seismic wave inside the earth occur, and why?
At the boundary between the mantle and inner core, as there is the greatest change in density
How does the amplitude of a wave relate to how much energy it contains?
The larger the amplitude, the larger the energy it carries
What is refraction?
A wave changing direction after entering a new medium
What is the range of hearing for humans called?
The auditory range (20-20,000Hz)
What are ultrasound waves?
Waves with a frequency greater than 20,000Hz
What is a special feature of ultrasound waves?
They partially reflect at the boundary between two different densities
What does a wave transfer?
Energy from one place to another
What causes a wave?
A vibration
What is the definition of a transverse wave?
A wave whose oscillations are perpendicular to the direction of energy transfer
What is the definition of a longitudinal wave?
A wave whose oscillations are parallel to the direction of energy transfer
What is a compression?
When the particles in a longitudinal wave are closest together
What is a rarefaction?
When the particles in a longitudinal wave are furthest apart
Give 3 examples of longitudinal waves
- P waves
- Sound waves
- Ultrasound waves
Give 3 examples of transverse waves
- S waves
- Water waves
- All electromagnetic waves
What the period of a wave?
The time it takes for a wave to complete one full oscillation
What is the frequency of a wave?
The number of waves passing a point each second
What direction from the normal do waves bend when they slow down?
When waves slow down they bend towards the normal
What direction from the normal do waves bend when they speed up?
When waves speed up they bend away from the normal
In what instance do waves not refract when entering a different medium?
When the waves meet/leave the medium at a right angle to the surface
Why is the frequency range of the human ear limited?
The conversion of sound waves to vibrations of solids only works over a limited frequency
Name the mediums that light travels fastest to slowest in
Gases, liquids, then solids
Name the mediums that sound travels fastest to slowest in
Solids, liquids then gases
What is the speed of sound?
343m/s
What are mechanical waves?
Waves that require a medium to propagate
Transverse and Longitudinal
Describe a method to measure the speed of waves on a string
- Connect a string over a pulley to a vibration transducer
- Connect a power pack/signal generator to vibration transducer and turn it on
- Adjust frequency of generator to produce clear waves on the string
- Count number of wavelengths on the string and divide by the distance they occupy to calculate mean
wavelength - Use v = fλ to calculate speed of the wave
