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space Flashcards

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Physics 101 flashcards AP® Physics flashcards
1
Q

what happens to a light source as you get further away?

A

Light source appear fainter at greater distances because the emitted light spreads over a larger area as it travels

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2
Q

What is the surface area of a sphere, and how does it relate to the distance of a star?

A

the surface area is 4xpixr^2, where r is the radius.
For a star, the radius is the distance between the star and earth

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3
Q

how is the radiation recieved at earth

A

the radiation is spread out equally through the area of 4 x pi x d^2

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4
Q

what is the equation for the inverse square law of flux?

A

F = L
————-
4xpixd^2
F= flux (intensity) (wm^-2)
L= Luminosity (w)
d= distance between the star and earth (m)

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5
Q

what are the assumptions does the inverse square law make?

A
  1. the power from a star radiates uniformly through space
  2. No radiation is absorbed between the star and the earth
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6
Q

what does this equation tell us

A

This equation tells us:
For a given star, the luminosity is constant
The radiant flux follows an inverse square law
The greater the radiant flux (larger F) measured, the closer the star is to the Earth (smaller d)

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7
Q

what is the principle of parrallax

A

it is based on how the position of an object appears to change as the position of observer changes

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8
Q

what is an example of parallex and what is it used for

A

stellar parallex
- can be used to measure the distance of nearby stars

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9
Q

what is the definition of stellar parallex

A

the apparent shifting in position of a nearby star against a background of distant stars when viewed from different positions of the earth during the earths orbit about the sun

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10
Q

what does stellar parallax involve

A

how the position of a nearby star changes over a period of time against a fixed background of distant stars
- from the observes position the distant stars dont appear to move
- this difference is creates the effect of stellar parralex

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11
Q

what is 1 AU and what is the value

A

it is the radius of the earths orbit around the sun it is 150,000,000 km

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12
Q

how do they use stellar parallax on earth to obseve distance to stars

A

The observations are made six months apart to maximise the distance the Earth has moved from its starting position
The Earth has completed half a full orbit and is at a different position in its orbit around the Sun
The nearby star will appear in different positions against a backdrop of distant stars which will appear to not have moved
This apparent movement of the nearby star is called the stellar parallax

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13
Q

what is the stellar parralax equation

A

tan p = AU
—–
d
For small angles, expressed in radians tan p = p
so
p= AU/d

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14
Q

definition of an arcsecond

A

it is 1/3600 degrees

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15
Q

definition of arc minute

A

1/60 degrees

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16
Q

how do arcsecond and parsecs relate

A

(parsec) d = 1/p (arcsec)

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17
Q

definition of a parsec

A

A parsec is the distance at which an object has a parallax angle of 1 arcsecond when observed from opposite sides of Earth’s orbit, separated by 1 astronomical unit (AU)

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18
Q

what is the value of 1 parsec

A

3.1 x 10^16m

19
Q

what is 1 light year = to

A

9.5 x 10^15m

20
Q

what is the definition of a standard candle

A

An astronomical object which has a known luminosity due to a characteristic quality possessed by that class of object

21
Q

what are the two types of standard candles are

A

cepheid variable stars
Type 1a supernova

22
Q

definition of apparent magnitude

A

how bright a star appears from our viewpoint

23
Q

definition of absolute magnitude

A

how bright a star is from from a fixed distance of 10pc

24
Q

what is the max distance you can use stellar parralex

A

1000 parsecs

25
Q

what is the type 1a supernova and why does it mean you can find the distance

A

A supernova explosion involving a white dwarf
The luminosity at the time of the explosion is always the same

26
Q

what is a cephied variable star

A

A type of pulsating star which increases and decreases in brightness over a set time period
This variation has a well defined relationship to the luminosity

27
Q

what is the advantage of using standing candles to measure distance

A

there is no distance limit as you can measure the period no matter how far you are

28
Q

whats the period equation in terms of distance

A

……………. _________
t = 2 x pi / r^3
/————–
/ Gx M

29
Q

What is the luminosity of a star?

A

Luminosity is the total energy a star emits per second in all directions, measured in watts.

30
Q

What does the luminosity depend on?

A
  1. Surface area (4 pi r^2) - larger starts emit more energy
  2. Surface temperature - hotter stars radiate more energy according to the stefan-boltzmann law
31
Q

What is the UV Catastrophe?

A

Classical theory predicted an infinite amount of energy as wavelength approached zero, which contradicted experimental data. where there is a drop at the ultra violet level.

32
Q

how does the uv catastrophe work?

A

At higher frequencies the energy of each
hf) becomes larger.
A system is less likely to have enough energy to produce these high-energy quanta.
This reduces the number of high-frequency photons emitted, causing the intensity to drop.

33
Q

what is wiens law

A

wavelength is inversely proportional to the absolute temperature

34
Q

what is wiens equation

A

lamba(peak) x T(emperature) = 2.898 x 10^-3 mk

35
Q

what is wiens constant

A
  • 2.898 x 10^-3 mk
36
Q

what is preferential scattering

A

preferential scattering (refraction) of Blue light (sky is blue) leaves yellow as the dominant colour we see from the disc

37
Q

what is the stefan boltzmann law

A

the relationship between surface temp and luminosity
L proportional T^4
also
L proportional to Area
so therefore
L= sigma x 4xpixr^2xT^4

38
Q

what is stefan boltzmanns constant

A

5.67 x 10^-8 Wm^-2K^-4

39
Q

what is the stellar cycle (small main sequence) ?

A
  1. star forming nebula
    2.protostar
    3.yellow star
  2. red giant
  3. planetary nebula
  4. white dwarf
  5. Black Dwarf
40
Q

what is the stellar cycle (Large main sequence) ?

A
  1. star forming nebula
  2. protostar
  3. Blue Giant
  4. Red supergiant
  5. super nova
    if massive
    - Black hole
    if just large
    - neutron star
41
Q

what happens in a star forming nebula?

A
  • it is a giant cloud of hydrogen gas and dust
  • gravitational attraction between atoms cause denser dumps of matter (gravitational collapse)
42
Q

what happens when it goes from a nebula to a yellow star?

A

Nuclear fusion
- eventually temp reaches millions of Kelvin and the fusion of hydrogen to helium begins

43
Q
A
44
Q
A

Physics (9 decks)

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