Waves And The Earth

Question 1

What is ultra sound

Answer 1

Sound Waves with frequencies over 20000 hz

Question 2

What are the uses of ultrasound

Answer 2

Prenatal scanning of a foetus
Waves can pass through the body but when they reach a boundary between two different media like fluid in the womb and the skin of the foetus some of them are reflected this can be processed by a computer to create an image

Sonar is used in the same way on ships to detect things in the water around them

Animals such as bats and dolphins also use this method
Other animals use ultrasound to communicate

Question 3

What is infra sound

Answer 3

Sound in a frequency lower than human hearing 20hz

They have long wavelengths so can travel long distances and move easily around objects

Question 4

What are the uses of infra sound

Answer 4

Elephants and tigers use infrasound to communicate

Meteor strikes and volcanic eruptions produce infra sound which means they can be detected far away

Question 5

Wave speed =

Answer 5

Distance(m)/time(s)

Question 6

What is the structure of the earth

Answer 6

Almost spherical
Thin crust
Mantle (solid that can flow slowly)
Core

Question 7

What are convection currents

Answer 7

The mantle moves very slowly up and away from the core and then cools and falls back down this pushes the tectonic plates around causing earthquakes

Question 8

How are seismic waves created

Answer 8

By earthquakes they travel through the earth

Question 9

What are p waves

Answer 9

They are longitudinal waves they travels fast and through solids and liquids

Question 10

What are S waves

Answer 10

They are transverse they only travel through solids and are much slower than p waves

Question 11

How do seismic waves give scientists an idea about the inside of the earth

Answer 11

S waves can only travel through through solids so they can’t be received behind the liquid core only to the sides after they reflect off the core
The p waves refract at every boundary this shows where the boundaries are and how the densities change.

Question 12

What is a seismometer

Answer 12

It records the p wave and S wave and how far apart they were this can give an idea as to how far away the epicentre is

Question 13

What is triangulation

Answer 13

There are 3 seismometers in an are and you drawing a circle around the point of the seismometer that is the distance away from the earthquake they are the point where all three circles meet is the epicentre of the earthquake
It only works if there are three seismometers in the area