Topic 4 - Waves And The Earth Flashcards
What is Pre-Natal Scanning ?
Ultrasound can pass through body but once reached a boundary between two medias the wave is reflected and detected
Not 100 sure it’s safe
Safer than x ray
What is ultrasound ?
20,000 Hz positive +
Partially reflected at a boundary between media
Some is transmitted = Partial Reflection
What is Sonar ?
Emit waves of ultrasound which reflect and they bounce back
Computers aboard work out time delays between the waves emitting and detecting there reflections
Speed = Distance / Time
What is Infrasound ?
Frequencies less than 20 Hz
Long wavelengths = long distances
Elephants use it to communicate
How do you calculate distance using ultrasound ?
Speed = distance / time
X = S. x. T.
What 5 parts make up the Earth?
Crust > Very Thin Inner Core > Solid Outer Core > Liquid Mantle > Solid but flows slowly Core > Made of iron and nickel
What is the earth surface like ?
Tectonic plates earth is made up Convection currents cause then to drift
Move a few cm per year
Whys it difficult to Predict earthquakes?
Very destructive and hard to predict
Sandpaper on surface with brick on top
Results show that earthquakes are unpredictable and can be any scale or size
Seismic waves . P Waves .
Longitudinal
Travel through liquids and solids
Travel faster than S Waves
Seismic waves . S Waves .
Transverse
Travel through solids
Slower than P Waves
What is Triagulation ?
3 circles on a map which will crossover at on point which is the epicentre
What is the current?
The rate of flow of charge around a circuit
What are electrons ?
Carry the charge (negatively charged particles)
