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A Level Physics > Cosmology > Flashcards

Cosmology Flashcards

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1
Q

What do the components of the Doppler effect equation mean?

A
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2
Q

What is the fractional change in wavelength also known as

A

the redshift

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3
Q

What does the redshift equation say about wavelength and frequency

A

if the source moves away from the observer then:
The wavelength increases
The frequency decreases

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4
Q

Draw a diagram showing the doppler shift of light

A
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5
Q

Describe what is observed (in terms of relative velocity and wavelength change) when a star approaches/ recedes from the earth

A
  • If the star is approaching the Earth, blueshift is observed (negative z):
    The relative velocity v is positive
    The change in wavelength increment lambda is negative
  • If the star is receding from the Earth, redshift is observed (positive z):
    The relative velocity v is negative
    The change in wavelength increment lambda is positive
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6
Q

Which type of light (red or blue) has a longer/shorter wavelength and frequency

A

red light - has a longer wavelength and a lower frequency
blue light - has a shorter wavelength and a higher frequency

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7
Q

eclipsing binary star system def

A

Where two stars orbit around a common centre of mass with their orbital plane in the Earth’s line of sight

They are always pi out of phase

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8
Q

By what can the stars in an eclipsing binary star system be identified by

A

from their characteristic light curves

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9
Q

Draw the light intensity curve of an eclipsing binary

A
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10
Q

Describe the primary and secondary minima on a light intensity curve of an eclipsing binary AND what they are caused by

A
  • The primary minima (the larger dip) are caused by the larger star passing in front of the smaller star
  • The secondary minima (the smaller dip) are caused by the smaller star passing in front of the large star
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11
Q

What does it mean when spectral lines from a distant galaxy are redshifted

A

The lines have shifted towards a longer wavelength, or towards the red end of the spectrum

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12
Q

Describe and draw a diagram for how we can observe the redshift of distant galaxies

A
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13
Q

Describe the expansion of the universe

A
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14
Q

What is the equation linking velocity, time period and radius of a binary star system

A
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15
Q

What is an eclipsing binary

A
  • binary star systems that orbit in the same plane as the line of sight
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16
Q

Quasars/ quasi-stellar object def

A

Extremely luminous star-like sources of radiation with very high redshifts

17
Q

What are quasars notable for

A
  • strong radio emissions
  • High luminosities
  • Extremely large redshifts
  • Small size
18
Q

Describe the formation of quasars

A
  • quasars are a type of active galactic nucleus, meaning they are supermassive black holes, surrounded by an accretion disc of matter
  • They are found at the centre of extremely distant galaxies
  • When they become active, i.e. when matter falls into it, they become quasars
  • As matter falls into the black hole, jets of radiation are emitted from the poles
  • The gravitational potential energy of infalling matter is transferred to electromagnetic radiation
  • Now it is known that quasars are strong emitters of all wavelengths, not just radio waves
  • Quasars are formed around black holes
  • When the black hole no longer has matter falling into it, the quasar will stop emitting radiation
19
Q

What does the high redshift of quasars explain about quasars and the universe

A
  • Quasars are thought to be some of the most distant measurable objects in the known universe
  • This allows astronomers to see very far back to an early Universe as it was not long after the Big Bang
20
Q

what is the absolute magnitude of the sun

A

5

21
Q

surface temperature of the sun

A

6000k

22
Q

star classification of the sun

A

class g

23
Q

What does Hubble’s law state

A

The recessional velocity of a galaxy is proportional to its distance from Earth

24
Q

Hubble’s law equation

A
25
Q

What does Hubble’s law show

A
  • The further away a star is from the Earth, the faster it is moving away from us
  • The closer a star is to the Earth, the slower it is moving away from us
26
Q

Describe Hubble’s law in relation to estimating the age of the universe

A
27
Q

What are the key 3 pieces of evidence for the Big Bang theory

A
28
Q

Describe what dark energy is and its controversy

A
29
Q

Describe the controversy concerning the behaviour of the universe

A
  • Measurements of supernovae do not agree with predictions from Hubble’s law
  • So the universe must be expanding at an increasing rate (it is accelerating)
  • This is controversial as there is no known energy source for expansion, or reference to dark energy

A Level Physics (33 decks)

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