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A level Physics > Astrophysics > Flashcards

Astrophysics Flashcards

(104 cards)

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1
Q

What defines a real image?

A

Formed at the point where scattered light converges; always inverted

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2
Q

When can a real image be produced?

A

When the object is further away from the lens than the focal point

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3
Q

What characterizes a virtual image?

A

Created by the appearance of convergence; cannot be projected onto a screen

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4
Q

When are virtual images visible?

A

When looking through a lens or mirror; not inverted

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5
Q

What is the lens equation relationship involving?

A

u = distance to the object, v = distance to the image, f = focal length

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6
Q

What is magnification in optics?

A

The ratio of the size of the object as it appears normally to the size in the image

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7
Q

How is magnification measured?

A

By comparing the angles subtended by the object with and without a telescope

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8
Q

What do refracting telescopes use to focus light?

A

Two converging lenses: the objective lens and the eyepiece

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9
Q

What does normal adjustment in a telescope mean?

A

The final image is at infinity; parallel rays emerge from the eyepiece

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10
Q

Who was the first person to use a refracting telescope for astronomy?

A

Galileo Galilei in 1609

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11
Q

What is chromatic aberration?

A

Occurs when different wavelengths of light are refracted by different amounts

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12
Q

How do reflecting telescopes avoid chromatic aberration?

A

By using mirrors instead of lenses to focus light

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13
Q

What is spherical aberration?

A

Occurs when a spherical mirror does not have a single focal point

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14
Q

What type of mirrors are now used to avoid spherical aberration?

A

Parabolic mirrors

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15
Q

What is collecting power in telescopes?

A

The rate at which useful energy is received, depending on the area of the collecting surface

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16
Q

What is resolving power?

A

The smallest angle at which a telescope can accurately discern two separate points

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17
Q

What is the Airy disc?

A

The interference pattern created when light passes through a circular aperture

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18
Q

What does the Rayleigh criterion state?

A

The minimum separation for two points to be clearly resolved occurs when the central maximum of one overlaps the first minimum of the second

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19
Q

What are Charge-Coupled Devices (CCDs)?

A

Sensitive light detectors made of semiconductor layers that capture photons

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20
Q

What is quantum efficiency in the context of CCDs?

A

The percentage of incident photons detected by the CCD for a given wavelength

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21
Q

How does the quantum efficiency of CCDs compare to the human eye?

A

CCDs can have a quantum efficiency of about 70% to 95%, while the human eye is about 1%

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22
Q

Fill in the blank: The first reflector telescope was built by ______ in 1668.

A

Isaac Newton

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23
Q

What is the main advantage of CCDs over the human eye?

A

They can be left ‘on’ for extended periods to detect fainter objects

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24
Q

What is the formula for magnification?

A

M = θ_image / θ_object

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25
What is the significance of the James Lick telescope?
An astronomical refracting telescope used in normal adjustment calculations
26
True or False: A virtual image can be projected onto a screen.
False
27
What is the diameter of the telescope's aperture referred to?
The diameter of the collecting surface
28
What problem does spherical aberration cause in telescopes?
It results in a lack of a single focal point, leading to blurred images
29
What is a proto-star?
A denser lump of dust in space that heats up and begins to glow due to gravity
30
What happens when a lump of dust reaches a few million degrees?
It begins to fuse hydrogen at the core and becomes a star
31
What are main sequence stars?
Stars that fuse hydrogen in the core
32
What occurs when hydrogen fusion stops in the core of a star?
The core collapses, becoming denser and hotter
33
What is a red giant?
A star that has left the main sequence and expanded due to hydrogen fusion occurring in outer layers
34
What happens to a star after all the helium is fused?
It may continue fusing heavier elements until it reaches iron
35
What happens when fusion stops in smaller stars?
They eject their outer layers, creating a planetary nebula and leaving a white dwarf
36
What is a white dwarf?
A small, dense, extremely hot core left after a star ejects its outer layers
37
What does a white dwarf do over time?
Radiates away thermal energy, eventually fading from white to black
38
What is a planetary nebula?
The outer layers ejected by a smaller star, misleadingly named as they have nothing to do with planets
39
What is electron degenerate matter?
Matter that cannot exist in its normal state due to immense density, stabilizing white dwarfs
40
What is the Chandrasekhar limit?
The maximum mass of an electron-degenerate object, approximately 1.4 solar masses
41
What occurs during a supernova?
A rapid collapse of a red super giant's core, causing an explosion of outer shells
42
How bright can a supernova be?
It can outshine its parent galaxy, radiating more energy than billions of stars
43
What elements are formed during a supernova?
Elements larger than iron in the periodic table
44
What is a neutron star?
A star created when electrons are forced into protons under extreme pressure, forming neutrons
45
What is the typical size of a neutron star?
About 20 kilometers across
46
What are pulsars?
Neutron stars that emit radio waves and appear to flash like a lighthouse
47
What defines a black hole?
An object whose escape velocity exceeds the speed of light
48
What is the event horizon?
The boundary around a black hole beyond which nothing can escape
49
What is a singularity?
A point in a black hole with infinite density
50
What is the Schwarzschild radius?
The distance from the singularity to the event horizon
51
What is Sagittarius A*?
The supermassive black hole at the center of the Milky Way
52
What is a red dwarf?
The smallest and coolest type of main sequence star that never enters the giant phase
53
What are spectral classes of stars?
Categories of stars based on their absorption lines: O, B, A, F, G, K, M
54
What causes absorption lines in a star's spectrum?
Particles in the star's atmosphere absorb specific wavelengths of light
55
What is the Balmer series?
A series of absorption lines in the visible part of the EM spectrum
56
What is the Hertzsprung-Russell diagram?
A graph that categorizes stars by absolute magnitude and spectral class
57
What are apparent and absolute magnitudes?
Apparent magnitude is brightness as viewed from Earth; absolute magnitude is brightness at 10 parsecs
58
What is black body radiation?
Radiation emitted by stars as near-perfect absorbers and emitters of light
59
What does Wien's law calculate?
The peak wavelength of emitted radiation based on temperature
60
What is Stefan’s Law?
A formula to calculate the luminosity of a star based on its surface area and temperature
61
What is intensity in terms of light?
Power per unit area following the inverse square law
62
What is an Astronomical Unit (AU)?
Distance from the Sun to the Earth
63
What is a Light Year?
Distance light travels in one year
64
Define Parsec.
Distance to an object with a parallax of one arcsecond
65
What is the method called that measures stellar distances using parallax?
Method 1: Parallax
66
What are background stars?
Stars that are so far away that they never move relative to closer stars
67
How is parallax measured?
By observing the apparent shift of nearby stars relative to background stars over six months
68
What unit is used to measure small angles in parallax?
Arcseconds
69
What is one parsec equivalent to in light years?
Approximately 3.26 light years
70
How many arcminutes are in a full moon's diameter?
About 30 arcminutes or 1800 arcseconds
71
What is apparent magnitude?
How bright an object appears from Earth
72
What is absolute magnitude?
Brightness at a distance of 10 parsecs
73
What are standard candles?
Objects with known absolute magnitude used to determine distances
74
What triggers a Type 1A supernova?
A white dwarf accreting mass from a binary companion until it reaches the Chandrasekhar limit
75
What is the Chandrasekhar limit?
Maximum stable mass for a white dwarf star
76
What defines the light curves of Type 1A supernovae?
A sharp initial peak followed by a gradually decreasing curve
77
What is an eclipsing binary?
A binary star system where two stars orbit a common center of mass
78
How does the brightness of eclipsing binaries vary?
It varies as one star passes in front of another
79
What significant distance measurement was achieved using eclipsing binaries?
The distance to the Large Magellanic Cloud
80
What are absorption lines?
Dark lines in a spectrum where specific wavelengths of light are absorbed by elements in a star's atmosphere
81
What does the Doppler Effect describe?
Compression or expansion of waves emitted from a source as it moves relative to an observer
82
What is red shift?
The phenomenon where light waves from an object moving away appear shifted toward the red end of the spectrum
83
What is the relationship between recessional velocity and distance in the universe?
Recessional velocity is directly proportional to how far away an object is
84
What is Hubble's Law?
The relationship defined by Hubble's constant between recessional velocity and distance
85
What is the approximate age of the universe?
About 15 billion years
86
What does Kepler's third law help calculate?
The distance from the Earth to the Sun
87
What is the Cosmological Principle?
The universe is homogeneous and isotropic, meaning it looks the same everywhere
88
What event marks the beginning of space and time?
The Big Bang
89
What happens during the recombination phase of the universe?
Electrons and protons combine to form neutral hydrogen atoms
90
What does the Cosmic Microwave Background Radiation (CMBR) represent?
The afterglow of the Big Bang, providing a snapshot of the early universe
91
What is a quasar?
A quasi-stellar object, often containing supermassive black holes
92
What methods are used to detect exoplanets?
* Transit method * Stellar wobble * Direct observation
93
What is dark matter?
A mysterious presence that cannot be seen but whose mass holds galaxies together
94
What is a major reason we cannot see planets clearly?
Planets are typically greatly outshone by their parent stars and are very far away.
95
What phenomenon suggests the existence of dark matter?
Objects in the universe orbiting one another too quickly.
96
What is dark matter?
A mysterious presence that we can’t see but whose mass holds everything together.
97
What are tachyons?
Hypothetical particles that travel faster than the speed of light.
98
Why can't we see tachyons?
They are theorized to be going back in time.
99
What was observed about the universe in the 1990s?
The universe was expanding at an accelerated rate.
100
What is required for acceleration to occur?
Energy.
101
What do we call the energy that is thought to be causing the universe's accelerated expansion?
Dark energy.
102
What percentage of the universe is thought to be made up of dark energy?
Approximately 68%.
103
What is the relationship between dark energy and dark matter?
Dark energy makes up a significant portion of the universe, while dark matter is another form of unseen mass.
104
Fill in the blank: Dark matter is a mysterious presence that we can’t see but whose mass holds everything _______.
[together]

A level Physics (14 decks)

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