P8.2 Powering Earth

Question 1

2 types of seismic waves

Answer 1

P (primary) waves and S (secondary) waves

Question 2

P waves

Answer 2

Longitudinal
Fast (5 km/s)
Can go through solids and liquids

Question 3

S waves

Answer 3

Transverse
Slower (3 km/s)
Can go through solids only

Question 4

Shadow zones

Answer 4

Where one or both types of waves are not detected

Question 5

Proof that Earth has a liquid outer core

Answer 5

Lack of propagation of S waves (shadow zones for S waves are present)

Question 6

Type of EM radiation stars emit

Answer 6

All but mainly visible light

It is a black body meaning it emits and absorbs every wavelength of EM radiation

Question 7

Relationship between temperature and wavelength

Answer 7

The hotter an object, the shorter wavelength peak it has

Question 8

What colour will hotter stars and cooler stars emit

Answer 8

Hotter - blue
Cooler - yellow and red

Question 9

3 main greenhouse gases

Answer 9

Carbon dioxide
Methane
Water vapour

Question 10

How greenhouse gases are NATURALLY released into the atmosphere

Answer 10

Volcanoes (CO2)
Respiration (CO2)
Oceans evaporating (H2O as steam)

Question 11

How greenhouse gases are released into the atmosphere due to HUMAN ACTIVITY

Answer 11

Combustion of fossil fuels (CO2)
Deforestation (CO2)
Extensive cattle farming (CH4)

Question 12

Explain greenhouse effect

Answer 12

Short wavelength visible light passes through the atmosphere mainly unobstructed. Some reflects from clouds.
Earth absorbs the radiation and heats up. It is warm enough to emit only long wavelength infrared radiation.
Infrared radiation is absorbed by greenhouse gases in the atmosphere.
This heats the atmosphere.
IR radiation absorbed by the atmosphere is then re-emitted in all directions. Some is emitted back to the Earth’s surface

Question 13

Force which works on all planets around the sun

Answer 13

Centripetal force
This force always acts towards the centre of the orbit
The force/acceleration must be at right angles to the direction of movement
The velocity is changing because the direction is changing, but the speed is constant

Question 14

Why are planets closer to sun able to move faster than objects away from sun

Answer 14

Since they are closer, they have a larger force of gravity working on it as it’s closer to the sun and likewise with the opposite according to the inverse square law

Question 15

Geostationary orbit satellites

Answer 15

Take 24 hours to orbit
Remain in fixed position above Earth’s surface
Orbit above Earth’s equator
Used for satellite communication

Question 16

Low polar orbit satellite

Answer 16

Have a very short time period (90 mins)
Travel pole to pole
Can observe every part of the planet over time
Relatively close to the Earth’s surface
Used as weather, mapping and spy satellites

Question 17

Life cycle of a stars (formation)

Answer 17

Interstellar gas clouds (nebulae) collapse due to gravity, producing a protostar
When a star is large and hot enough, it starts to fuse hydrogen into helium in its core
This is when a star is stable: the main sequence star

Question 18

Life cycle of a stars (death of small stars like the sun)

Answer 18

Smaller stars, like the sun, expand and cool to become red giant stars
They lose their outer gas layers to produce planetary nebula.
Centre of the red giant star collapses and forms a small and hot white dwarf star
Cools to form a brown dwarf then a black dwarf

Question 19

Life cycle of a stars (death of larger stars)

Answer 19

Larger stars expand and cool and become red supergiant stars
Centre of the star continues to collapse until it explodes in a supernova explosion
Remaining star then collapses to form a neutron star or a black hole if the star is that large
Black holes have such a large mass and large gravity that not even light can escape

Question 20

Evidence of the Big Bang

Answer 20

Doppler effect
Cosmic background radiation

Question 21

Doppler effect

Answer 21

Light from all far away galaxies is red shifted
Shows that the galaxies are moving away from us
The further away a galaxy is, the more its light is red shifted and the faster it is moving away from us
Therefore, if you put it in reverse, it would mean that the universe was much closer together at one small dense point

Question 22

Cosmic microwave background radiation (CMBR)

Answer 22

In the 1960s, scientists discovered that microwave radiation was coming from all directions of the universe
This radiation is believed to be the heat radiation that is left over from the original explosion
This radiation had a high frequency but as it has been stretched over time, it now has a frequency in the microwave region of the EM spectrum