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A Level Physics > Astrophysics > Flashcards

Astrophysics Flashcards

1
Q

Define planet:

A

an object with sufficient mass for its own gravity to make it spherical and clear the orbit of other objects

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2
Q

Define dwarf planet:

A

orbit not cleared of other objects

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3
Q

What are planetary satellites?

A

bodies that orbit a planet

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4
Q

What are asteroids?

A

objects that are too small and uneven to be planets, near circular orbit to sun

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5
Q

What are comets?

A

small, irregular sized balls of rock, dust, and ice; have an eccentric elliptical orbit around the sun

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6
Q

What are solar systems?

A

group of stars and orbiting objects

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7
Q

What are galaxies?

A

collection of stars (around 100 billion), dust and gas

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8
Q

What is the doppler effect?

A

apparent shift in wavelength occurring when the source of the wavelength is moving

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9
Q

What happens to the wavelengths according to the doppler effect?

A

wavelength emitted remains the same, wavelength received changes

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10
Q

What is the formation of a small star?

A

nebula > protostar > main sequence > red giant > white dwarf > black dwarf

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11
Q

What is the formation of a large star?

A

nebula > protostar > main sequence> super red giant > supernova > (supermassive) black hole/ neutron star

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12
Q

Which pressures are balanced in main sequence?

A

gravitational and radiation

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13
Q

How heavy is a star for it to be a large star?

A

greater than 10 mass units

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14
Q

How heavy is a star for it to be a small star?

A

between 0.5 to 10 mass units

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15
Q

When can electrons bound to an atom exist?

A

in certain energy levels

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16
Q

What is needed when moving an electron to a higher energy level?

A

external energy (heat/ absorbing a photon)

17
Q

What happens when an electron moves to a lower energy level?

A

releases a photon with specific wavelength

18
Q

What is the lowest energy level?

A

ground state

19
Q

What is the energy of an electron free of an atom?

A

0J

20
Q

Why is energy change between levels negative?

A

it is the energy required to remove the electron from the atom

21
Q

What is Wein’s law?

A

the black body radiation curve for different temperatures peaks at a wavelength inversely proportional to the temperature of the object

22
Q

What does the peak of Wein’s graph represent?

A

temperature

23
Q

What does the x axis of Wein’s graph represent?

A

wavelength

24
Q

What is Stephan’s Law?

A

radiant heat energy emitted from a surface is proportional to temperature^4

25
Q

List light years, parsecs and astronomical units in smallest to largest:

A

astronomical units, light years, parsecs

26
Q

What unit is a parallax angle measured in?

A

arcsec

27
Q

What are parallax angles used to find?

A

unknown distances that stars are away

28
Q

What is the cosmological principle?

A

the universe is isotropic and homogenous and the laws of physics are universal

29
Q

What does isotropic mean?

A

same in all directions

30
Q

What does homogenous mean?

A

matter is universally distributed

31
Q

What is Hubble’s law?

A

recessional velocity of a galaxy is proportional to it’s distance from the earth

32
Q

What does Hubble’s law show?

A

the universe is expanding and distance from galaxies are redshifted (moving away from earth)

33
Q

What is the big bang theory?

A

all objects were initially a singularity

34
Q

What is the evidence for the big bang?

A

Hubble’s law (universe expanding) and background microwave radiation

35
Q

What happened in the evolution of the universe?

A
  • Big Bang: time and space created
  • 10^-35s: inflation
  • 10^-6s: fundemental particles gain mass
  • 10^-3s: mass created via pair production (hadrons and leptons)
  • 1s: production of mass halted
  • 100s: protons and neutrons fuse
  • 380,000 years: first atom
  • 30 million: stars formed + fusion for heavier elements
  • 200 million: galaxies form and gravitational fields pull hydrogen and stars together
  • 9 billion: solar system formed
  • 10 billion: sun and earth formed
  • 11 billion: life on earth
  • 13.7 billion: humans
36
Q

What is dark matter?

A

hypothetical form of matter that fills space and accelerates expansion and shows there is no centre to the universe

A Level Physics (22 decks)

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