P1: Flashcards
Give the features of S waves?
S waves only travel thought solids. This tells scientists that the earths core is liquid.
S waves are transverse because they travel in right angles from the direction of the wave.
Give the features of P waves
P waves travel through solids and liqurds.
They are also refracted by the core.
P waves are longitudinal because they travel in the same direction as the waves travel in.
What is used to detect P&S waves?
Seismometer
What causes the skin to tan ?
Skin cells produce melanin: a pigment which produces a tan.
People with darker skin do not tan easily, why ?
The UV radiation gets filtered out.
Explain Ozone depletion.
Ozone is found in the stratosphere.
It helps filtering out UV radiation.
CFCs destroy the ozone and reduces thickness of the ozone.
This could be very dangerous to humans.
The ozone layer is thinness above the south pole because ozone depleting chemicals work best in the cold.
There is an international agreement to reduce CFCs.
Satellites are used to monitor the thickness of the ozone layer.
Radio waves are reflected and refracted in the Earths atmosphere.
Give a factors of which determine the amount of refraction?
Frequency of the wave. There is less refraction at higher frequencies.
The same frequency can be used by more than one radio stations. So what happens ?
The radio waves are too far away from each other to interfere.
Unusual weather conditions causes radio waves travel further and the broadcasts interfere.
How can interference be reduced?
By using digital signals.
What are the advantages and disadvantages of DAB radio?
Ad: more stations available
Eliminates interference and clearer signal.
Dis: not all of UK is covered
Sound quality may not be as good as FM
What reflects radio waves back into the earth?
The ionosphere
What does radio waves undergo when being reflected ?
Total internal reflection.
Water reflects radio waves but what doesn’t?
Land mass
Continued reflection from the ionosphere and oceans results in…..
Allows radio waves to be received from aerials which are not in a line of sight.
