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GCSE OCR Physics > P7 - Further Physics - Studying the Universe > Flashcards

P7 - Further Physics - Studying the Universe Flashcards

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1
Q

What is 1’ arc minute?

(1’ minute of arc)

A

1/60*1o.

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2
Q

How are stars formed?

A
  1. Gravity brings gas clouds together, causing them to become denser.
  2. The force of gravity pulls the gas inwards, causing the pressure and temperature to increase.
  3. As more gas is drawn in, the force of gravity increases.
  4. The gas is compressed further, becomes hotter and denser, and forms a protostar.
  5. Eventually, the temperature and pressure become so high that hydrogen nuclei fuse into helium nuclei. Energy is released and the star is a main sequence star.
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3
Q

What is retrograde motion?

A

Where planets appear to slow down against the star background and go in reverse.

This happens because the Earth’s smaller orbit causes it to overtake the outer planets at different times of year.

A good example is Venus, which looks like it travels in one direction when on the same side of the Sun as Earth, but the opposite direction if it’s on the other side to Earth.

See this video to visually explain this concept.

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4
Q

How long does it take for the Moon to orbit the Earth?

A

About 27 days.

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5
Q

What is 1’’ arc second?

(1’’ second of arc)

A

1/60*1’ or 1/3600.

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6
Q

What are the properties of diffraction?

A
  • None of the properties change apart from the direction in which the wave is travelling.
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7
Q

Draw the Lifecycle of a Star.

A
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8
Q

Give advantages and disadvantages to locating astronomical observatories on isolated high mountains.

A

_Advantages *(Any of the following)*:_

  • Away from any light pollution.
  • Low atmospheric pollution.
  • Less scattering of light.
  • Dry air/less humid.
  • Frequent cloudness lights/above the clouds.
  • Less atmospheric absorption.
  • Less atmospheric refraction.
  • Darker skies give more contrast.
  • Less image distortion/flickering.

_Disadvantages *(Any of the following)*:_

  • Still some atmospheric absorption.
  • Still some atmospheric refraction.
  • Some parts of em spectrum absorbed by atmosphere.
  • Altitude sickness/difficult working conditions.
  • Hard to get to location.
  • Higher construction/transport costs.
  • Poor transport links.
  • Environmental and social impacts.
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9
Q

You are given the following formula. What are the units?

Speed of recession = Hubble constant * Distance.

A

Speed of recession (km/s) = Hubble constant (s-1) * Distance (km).

AND

Speed of recession (km/s) = Hubble constant (km s-1 Mpc-1) * Distance (Mpc).

N.B: -1 means per. For example, km s-1 Mpc-1 means kilometers per second per megaparsec.

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10
Q

State two major ground-based optical telescopes.

A
  • Royal Observatory, UK.
  • Mauna Kea Observatories, Hawaii.
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11
Q

There is a relationship between cepheid period (days) and absolute brightness (lux) - what is this?

A

Henrietta Leavitt’s graph showing as the period increases, absolute brightness increases.

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12
Q

What are the ways we can calculate the distance of stars?

A

We can either use red shift to calculate the velocity of recession (km/s) and therefore the distance using Hubble Law’s graph.

OR

We can use a parallax distance (Convert from parsecs to megaparsecs). That’s it! We could also use Hubble Law’s graph though, to get the velocity of recession (km/s).

OR

We can calculate the period of luminosity from a cepheid, then calculate the absolute brightness through Henrietta Leavitt’s graph and then use the equation Distance+Apparent Brightness=Absolute Brightness (You will need the apparent brightness, and rearrange the equation).

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13
Q

What is a virtual image?

A

The image formed when light rays from an object appear to have come from another point. e.g: A mirror. The image can not be captured on a screen, as the light waves never cross.

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14
Q

What are the 5 steps to drawing a ray diagram?

A

1) Draw the first ray line from the top of the object to the lens. Then, carry it through the focus.
2) Draw the second ray line from the top of the object through the principal axis (Centre of lens), and carry it on.
3) Draw the third ray line from the top of the object through the focal point on the same side, through to the lens and then horizontally.
4) If the object crosses the principal axis, draw a fourth ray horizontally from the bottom of the object parallel to the principal axis. Then, at the lens, bend the ray towards the focal point on the opposite side.

— The 3 rules —

  • In parallel, out through focus.
  • In through focus, out parallel.
  • Straight through vertex.
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15
Q

If nuclear fusion only occurs up to iron - how come we have elements with higher masses than iron?

A

Because when a high mass star’s core is mostly iron, it explodes as a supernova, creating nuclei with masses greater than iron.

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16
Q

In the Curtis & Shapley debate - What did Shapley say?

A

That the nebulae were nearby within the Milky Way, and that the universe contained only one big galaxy.

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17
Q

Electromagnetic radiation with a higher frequency will refract more/less?

A

Electromagnetic radiation with a higher frequency will refract more?

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18
Q

What is 1 parsec?

A

The distance to a star with a parallax angle of one second of arc.

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19
Q

What is the purpose of the objective lens?

A

To form an image, therefore it should have a long focal length (So that the image can go deeper into the eyepiece without losing focus) and large diameter (To gather more light).

This may seem weird, since it means it has little power, but actually using the formula focal length of objective lens/focal length of eyepiece lens, we can see that the bigger the difference, the higher the magnification, and that if the objective lens had the shortest focal length, we would have a negative magnification.

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20
Q

Compare nuclear fusion in main sequence stars and red giants.

A
  • Main sequence stars fuse hydrogen to helium.
  • Red giants have a contracting core and rising temperature, so helium can fuse to carbon and further reactions to produce heavier nuclei occur.
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21
Q

Convert 0oC to K.

A

0oC = 273K.

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22
Q

What are the units for pressure?

A

Pa (N/m2).

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23
Q

A lens that is more curved than another lens made from the same material is stronger/weaker in power and has a shorter/longer focal length?

A

A lens that is more curved than another lens made from the same material is stronger in power and has a shorter focal length?

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24
Q

What is a real image?

A

The image formed when light rays from an object are made to pass through another point. The light rays are actually there and the image can be captured on a screen.

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25
Q

To convert from Co to Ko, you __________ 273.

A

To convert from Co to Ko, you add 273.

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26
Q

When white light is passed through a prism, the light is refracted.

_________ light is refracted the least, and _________ light is refracted the most.

A

red light is refracted the least, and violet light is refracted the most.

This is because the colours that make up white light have different frequencies and wavelengths.

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27
Q

How do you calculate the luminosity period of a cepheid?

A

1/Frequency of pulses

(Not given).

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28
Q

To convert from Ko to Co, you _________ 273.

A

To convert from Ko to Co, you subtract 273.

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29
Q

What is parallax?

A

The apparent motion of an object against a background.

It’s actually the motion of the observer that causes the parallax motion of an object, however.

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30
Q

Define diffraction.

A

When waves move through a narrow gap or past an obstacle, and spread out from the edges.

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31
Q

How long does it take for the Earth rotate 360o on its west-east axis?

_Accurately_. What is this called?

A

23 hours and 56 minutes.

Sidereal day.

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32
Q

Red light has a __________ wavelength and a _________ frequency compared to violet light.

A

Red light has a long wavelength and a low frequency compared to violet light.

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33
Q

Define mass.

A

The amount of matter.

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34
Q

How do you calculate absolute brightness?

A

Distance + Apparent brightness = Absolute brightness.

(Rearrangeable - not given)

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35
Q

What evidence of extraterrestrial life have scientists found?

A

None.

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36
Q

What must you have to confirm a causal link?

A

A mechanism that explains how the factor causes the outcome.

37
Q

What must astronomical observatories be aware of in order to be socially acceptable.

A
  • Costs involved.
  • Environmental and social impact nearby.
  • Working conditions for employees and access.
38
Q

How big is 1Mpc?

A

1Mpc = 1 mega-parsec = 1 million parsecs.

39
Q

Diffraction is at its maximum when…

A

Diffraction is at its maximum when gap in aperture = wavelength.

To minimise diffraction, the gap in aperture should be larger than the wavelength.

40
Q

What is absolute zero?

A

-273oC / 0oK.

This is the point at which particles stop moving altogether, and have no more energy to lose, and the temperature can not get any lower.

41
Q

What is a total solar eclipse?

A

When the moon is directly in front of the Sun, and completely obscures the Earth’s view of the Sun, casting a shadow on the Earth.

42
Q

What are the positives and negatives to Reflecting telescopes?

A

Positives

  • Chromatic aberration does not occur.

Negatives

  • Many designs - different positioning and function of secondary mirror.
43
Q

Give 4 examples of major astronomical observatories.

A
  • Hawaii.
  • Australia.
  • Chile.
  • Canary Islands.
44
Q

How is global success important in astronomy?

A

Share the cost

  • Expensive. e.g: The Great Canary Telescope of 2009, funded by Spanish Government, Mexico and Florida.

Share expertise

  • Work faster, more efficiently and share ideas.

Global access

  • Astronomers can book time on telescopes in different countries, allowing them to see the stars on the other sides of the Earth.
45
Q

Hubble law and cepheids both rely on different factors - what are these?

A

Hubble law depends on cepheid variable distances.

Explanation: The Hubble Constant is accurately calculated because we know how far away the cepheid variable stars are.

Cepheid variable distances depend on parallax distance.

Explanation: We can use cepheid variable distances when we can’t use parallax. Also, some scientists have tried to combine marginal measurements of many Cepheids to derive an “average” parallax.

46
Q

How can we tell what chemical elements a star contains?

A

By comparing the emission spectra of elements with the absorption spectra of a star.

47
Q

State and explain the 3 main parts of a star.

A
  • Core - Hottest part of the star where nuclear fusion takes place and energetic photons are released.
  • Convective zone - Where energy in the form of photons is transferred to the surface by convection currents.
  • Photosphere - Where photons are radiated into space.
48
Q

Radiation is diffracted by the aperture of a telescope - how do we get around this?

A

The effect of this is blurry images.

To make sure images are sharp, the aperture must be much larger than the wavelength of the radiation detected by the telescope.

49
Q

Draw the Hertzsprung-Russell Diagram.

A
50
Q

Define reflection.

A

When a wave bounces from the surface of an obstacle.

51
Q

What are the positives and negatives to putting telescopes in space?

A

Positives

  • Avoid atmospheric absorption/reflection/distortion.
  • Can use parts of spectrum that atmosphere absorbs.

Negatives

  • Lots of money to set up, maintain and repair.
  • Uncertainties of space program.
52
Q

What do astronomers use to get spectrums from stars?

A

A spectrometer.

53
Q

A large or hot star will burn bright/dim?

A

A large or hot star will burn bright.

Therefore, further stars may appear brighter.

54
Q

What is a lunar eclipse?

A

When the Earth is between the Sun and the Moon. This results in the Earth casting a shadow on the Moon.

55
Q

What features do major astronomical obervatories have?

A
  • Little rain (Avoid defraction from rain).
  • High elevation (To avoid atmospheric distortion).
  • Frequent cloudless nights (To see stars clearly).
  • Low atmospheric pollution + dry air (To see stars clearly).
  • Low light pollution (Darker skies provide more contrast).
  • Equitorial location (Best view of solar eclipses).
  • Less scattering of light.
  • Less image distortion/flickering.
56
Q

What is an extrasolar planet?

A

A planet that orbits a star other than the Sun.

57
Q

Define refraction.

A

When waves cross a boundary between one medium and another.

58
Q

What is a solar eclipse?

A

When the Moon passes between the Earth and the Sun, causing a shadow on Earth.

59
Q

How long does it take for the Earth rotate 360o on its west-east axis?

Roughly. What is this called?​

A

24 hours.

Solar day.

60
Q

If the Moon orbits the Earth approximately every month, why don’t eclipses occur every month?

A

Because the moon doesn’t orbit on the same plane as Earth - it has a 5o inclination to that of the Earth.

Therefore, eclipses only occur when the Moon passes through the ecliptic (The apparent path the Sun traces out along the sky).

61
Q

What does a stars luminosity depend on?

A
  • Size.
  • Temperature.
62
Q

What are the positives and negatives to refracting telescopes?

A

Positives

  • One basic design.

Negatives

  • Chromatic aberration occurs (That weird RGB thing that looks quite cool actually).
  • Expensive at large sizes.
  • Some of the light reflects off the lens, so the image is very faint.
63
Q

Why do we use computers in telescopes?

A
  • Work remotely.
  • Continuous tracking of astronomical objects.
  • Precise positioning towards astronomical objects.
  • Storage and processing of data.
64
Q

In the Curtis & Shapley debate - what did Curtis say?

A

That nebulae were made up of many stars, and that the universe consisted of many galaxies like our own, and that fuzzy objects were distant galaxies.

He was correct. This was proven by improved telescopes and the fact that Edwin Hubble observed Cepheid variables in one nebula, and found that the nebula was much further away than any star in the mily way.

65
Q

What is a parsec?

A

The distance to a star with a parallax angle of one second of an arc.

66
Q

Why does the moon turn red during a lunar eclipse?

A

Because the atmosphere filters out the green to violet range of the spectrum, letting the red light pass through. Also, the Earth’s atmosphere refracts the light so that it is bent slightly, and can illuminate the moon at the greatest eclipse (The instant when the axis of the Moon’s shadow passes closest to the center of Earth).

67
Q

What is Declination?

A

Declination is like latitude, it reports how far away a star is from the celestial equator.

  • A positive declination is visible from the northern hemisphere.
  • A negative declination is visble from the southern hemisphere.

You should also be aware that right ascension is the angular distance measured along the celestial equater. It is measured in hours.

68
Q

Write a sequence of equations to explain how Helium (4,2) is formed.

A
69
Q

What does a stars observed intensity depend on?

A
  • Luminosity (Actual brightness).
  • Distance from Earth.
70
Q

What are the properties of reflection?

A
  • None of the properties change apart from the direction in which the wave is travelling (Inverted, > becomes < ORA).
71
Q

What is angular magnification?

A

The increase in the angle of an object, which makes it seem larger than it actually is. This is due to refraction of light.

72
Q

Define volume.

A

A 3D amount of space.

73
Q

What are the properties of refraction?

A
  • The frequency remains the same.
  • There is a change in wavelength.
  • Consequently, there is a change in wave speed.
  • Consequently, there is a change in direction.
74
Q

Describe the journey of light in a refracting telescope.

A
  1. Light enters through the objective lens, which is usually a convex lens.
  2. Light is defracted slightly.
  3. Light hits the eyepiece lens, which is usually a concave lens.
  4. The image is magnified.
  5. Light hits the users eye.
75
Q

Why is a sidereal day shorter than a solar day?

A

Because the Earth also orbits the Sun, this orbiting movement is the cause.

76
Q

Describe the journey of light in a reflecting telescope.

A
  1. Light enters and hits the rear primary mirror, which is the “objective lens”, and is usually a concave mirror to allow more light collection.
  2. Light is defracted slightly.
  3. Light hits the secondary mirror, which is the “eyepiece lens”, and is usually a diagonal mirror.
  4. Light hits the eye of the user.
77
Q

What are the units for volume?

A

m3.

78
Q

What are the units for mass?

A

kg.

79
Q

Define pressure.

A

The force per unit area on the walls of its container.

80
Q

How can we measure absolute brightness from parallax?

A
  1. Perform parallax.
  2. Get the distance to a star.
  3. Measure the stars apparent brightness.
  4. Distance+Apparent brightness=Absolute brightness!
81
Q

……What causes the emission of radiation of different frequencies (Line spectra)?

A

The movement of electrons within an atom.

Electrons can gain energy to move to a higher energy level, and will then release light of one wavelength when they return to the lower energy level.

82
Q

If you are asked to draw a graph (Oh no…) showing the relationship of stars for heat and colours, what would your X and Y axis be?

A
  • The X axis would be Wavelength (mm).
  • The Y axis would be Spectral Radiancy/Intensity.

Also, I would start at 3000K and go up in 1000K.

83
Q

What objects have scientists found in Space that makes it much more likely that extraterrestrial life exists?

A

Planets around other stars, some of which in other solar systems.

As well as this, we have found some planets similar to Earth.

84
Q

Describe The Celestial Sphere.

A

The Celestial Sphere is a grid for locating stars, relative to the Earth’s orbit.

Its x axis is right assention, measured in hours.

Its y axis is declination, measures in degrees north (+) and south (-).

1 hour = 15o.

85
Q

What is the parallax angle?

A

Half the angle moved against a background of distant stars in 6 months.

86
Q

Good ‘ol Jane looks at the moon when it is directly above her. She then looks in the same direction again 24 hours later - but the moon is not directly above her.

Why is this?

A

Because it takes longer for the moon to orbit the Earth than it does for the Earth to spin 360o on its axis.

87
Q

How can we prove that light and sound are waves?

A

Because they can be diffracted.

88
Q

What is the purpose of the eyepiece lens?

A

To magnify the image formed at the objective lens. Therefore, we want the most powerful lens here, which will have a short focal length.

GCSE OCR Physics (8 decks)

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