igcse physics astrophysics

Question 1

the sun

Answer 1

-a huge glowing ball of gas (a star)
-extremely hot, 6000°C on surface and 15,000,000°C in its center
-energy is released by nuclear reactions in its core
-most of its energy is radiated as infrared, visible and UV rays

Question 2

the earth

Answer 2

-turns slowly on its axis once a day
-half of the earth is in sunlight and half in shadow
-as it moved from light to shadow, it passes from day into night
-only planet that supports life

Question 3

temperatures of regions of the earth

Answer 3

area A and B can receive the same amounts of energy but on different surface areas.
the more spread out the energy, the less thermal energy there is as it is less concentrated.

Question 4

earth’s movement

Answer 4

-it moves around the sun in circular paths (orbits) which take 365 days
-earths axis is tilted by 23.5°
-which causes regions on earth to get varying hours of daylight/ varying climate condition and seasons throughout the year

Question 5

two reasons for the higher temperature in summer

Answer 5

• because of the tilt, the surface may be more concentrated in energy
  -more hours of sunlight

Question 6

season

Answer 6

1. December: winter in north, summer in south
2. March: equal hours of day and night
3. June: summer in north, winter in south
4. September: equal hours of day and night

Question 7

the moon

Answer 7

-smaller than earth
-moves around earth in a near-circular orbit
-each orbit takes 27.3 days to turn once on its axis (so moon keeps the same face towards us)
-surface of the moon reflects sunlight, allowing us to see it, the rest of the surface is in shawdows

Question 8

orbital speed

Answer 8

distance= 2πr
speed= d/T
r=3.84x10^5
T=27.3 days/ 655.2 hours
s= 3.68x10^3

Question 9

the solar system

Answer 9

-planets are not hot enough to give off their own light, so they’re only seen when it is reflecting sunlight
-planets are kept in orbit by the gravitational pull
-planets travel around the sun in the same direction and almost same plane
-the further a planet is from the sun, the slower it travels and more time it takes to complete an orbit, and the lower its average surface temperature

Question 10

the inner planets

Answer 10

Mercury
Venus
Earth
Mars

Question 11

the outer planets

Answer 11

Jupiter
Saturn
Uranus
Neptune
Pluto

Question 12

Mercury

Answer 12

-closest to the sun
-crated surface
-no atmosphere

Question 13

Venus

Answer 13

-brightest object in the night sky
-almost same size as earth
-covered by thick clouds of sulfuric acid
-its atmosphere causes a greenhouse effect (97% CO2)

Question 14

Mars

Answer 14

-called red planet bcs of its surface color
-has an atmosphere, dusty surface, and polar caps
-water may once have flowed there
-has no active volcanoes

Question 15

Jupiter

Answer 15

-more massive than all other planets put tgthr
-mainly gas, its atmosphere has 90% hydrogen and has no solid surface
-one of its moons have active volcanoes

Question 16

Saturn

Answer 16

-mainly gas
-surrounded by very thin rings (millions of pieces of ice ranging in size which orbit around it)

Question 17

Uranus

Answer 17

-gas giant
-has rings that are much fainter than Saturn’s
-its axis rotation is tilted at more than 90°

Question 18

Neptune

Answer 18

-outermost of the gas giants
-has faint ring system

Question 19

Pluto

Answer 19

-small in size
-most astronomers don’t consider it a main planet

Question 20

Comets

Answer 20

-highly elliptical orbits, in some cases can take them beyond Pluto and then close into the sun
- there is icy lumps (several of kms long) in the heads of the comments
-has a tail (millions of kms) from sun heat, dust and gas, which is visible bcs of sunlight reflection

Question 21

meteor

Answer 21

earth runs into tiny grains of material which hit the atmosphere so fast that they burn up, which causes a streak of light

Question 22

meteorite

Answer 22

a large chunk of material reaches the ground without completely burring up

Question 23

objects in the orbit

Answer 23

• each mass can attract other mass by gravitational force, so any object will go in a circular track in the orbit

Question 24

gravitational force depends on..

Answer 24

mass (directly)
distance squared (inversly)

Question 25

satellite

Answer 25

-orbits around more massive objects
-in a low orbit, it needs higher speed and vice versa
-a satellite in a geostationary orbit will always seem like its in the same position from the ground, bcs its period of orbit matches with the earths rotation, the distance is 35900 km so it will need a speed of 11100km/h

Question 26

light years equation

Answer 26

distance travelled by light in one year
d= speed (3x10^8) x time(365x24x60x60)
d= 9.5 x 10^10 km
-means that a start will take this many years to reach us

Question 27

galaxy

Answer 27

-galaxy contains a large number of stars including the sun
-between stars there is a thing spread gas and dust called interstellar matter
-over galaxy is called milky way
-a billions of galaxies = universe

Question 28

big bang theory evidence

Answer 28

galaxies appear to moving parts, they may once have been tgthr in the same space

Question 29

the big bang theory

Answer 29

• it was not an explosion into existing space, space itself started to expand
  -galaxies separating bcs the space between them is increasing

Question 30

the universe as balloon

Answer 30

as balloons inflates, all the parts inside appear to move away from each other. the more the distant, the faster they recede
-no single galaxy is at the center of expansion

Question 31

age of the universe

Answer 31

1/ Ho
Ho= 2.3x10ˉ¹⁸
so = 4.3 x10¹⁷ seconds

Question 32

red shift

Answer 32

-objects move away from the earth at high speed, light waves become stretched out, so the wavelengths shift toward the red

Question 33

blue shift

Answer 33

-objects move toward the earth at high speed, light waves become, so wavelength is shifted towards the blue

Question 34

expanding universe

Answer 34

light from distant galaxies is red shifted, so they are moving away from us, so we are living in an expanding universe

Question 35

doppler effect theory

Answer 35

-the universe and time began many billions of years ago from a single hot superatom erupted in a burst of energy called the big bang
this is where all the matter in the universe came from

Question 36

birth of a star

Answer 36

1.starts life as a cloud of dust and gas called nebula, then its collapsed by gravity
2.protostar: more temp, so faster movement of particles
3.nucleur fusion: hydrogen nuclei join tgthr to form helium nuclei
4.main sequence star stage

Question 37

death of stars (same size of the sun)

Answer 37

1. hydrogen starts to runs out
   2.outward force due to fusion is less than inward force of gravity
   3.star collapses inward, temp increases
   4.helium nuclei fuse tgthr, star expands forming a red giant
   5.helium nuclei stops to fuse forming a white dwarf
   6.cools down bcs no energy forming a black dwarf

Question 38

death of star larger than the sun

Answer 38

1.hydrogen nuclei runs out
2.helium nuclei fuse tgthr forming a red super giant
3.red super giant expands and explodes called a supernova, this makes elements heavier than iron
4.either becomes black mole or neutron star