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Aqa Physics > Astrophysics > Flashcards

Astrophysics Flashcards

(79 cards)

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1
Q

What is the principal axis ?

A

The horizontal axis which passes through the centre of the optical lens perpendicular to the lens axis

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2
Q

What is the principal focus ?

A

Single point were parallel incident rays converge (same distance on either side of the lens )

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3
Q

What is the focal length ?

A

The distance between the optical centre and the focal point

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4
Q

What is the focal plane ?

A

The plane perpendicular to the principal axis that contains the principal focus

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5
Q

What is the axial rays ?

A

Rays which are parallel to the principal axis. These rays always converge on the principal focus

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6
Q

What type of rays converge on the principal axis ?

A

Axial rays

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7
Q

What rays converge along the focal plane ?

A

Non axial rays

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8
Q

What is a lens ?

A

A transparent piece of glass or plastic with a curved surface to refract light

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9
Q

What is a convex lens ?

A

Lens that is narrow on the edges and the widest in the centre

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10
Q

What is a concave lens ?

A

A lens where the thickest part is the edges and the narrowest at its centre

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11
Q

What are the steps to draw a convex ray diagram ?

A

1- parallel to the axis refracts through f ( principal focus )
2- through f refracts parallel to the axis
3- through the centre remains affected

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12
Q

How can calculate magnification ?

A

Magnification = image height / object height

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13
Q

What is an upright image ?

A

When the image is the same way up as the object

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14
Q

What is an inverted image ?

A

If an image is upside down in comparison to the object

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15
Q

What is a real image ?

A

Rays which intersect on the opposite side of the lens

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16
Q

What is a virtual image ?

A

When the rays appear to come from a point of intersection on the same side of the lens

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17
Q

What type of object is produced for a concave lens ?

A

Virtual / upright /diminished

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18
Q

What is the image produce when the object is beyond two focal lengths?

A

Real / diminished / inverted

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19
Q

What is the image produced at 2f ?

A

Real / inverted / equal in size to the object

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20
Q

What is the image produced when the object is between 2f and f ?

A

Real / inverted / magnified

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21
Q

What is the image produced when the object is between the lens and the primary focus ?

A

Virtual / magnified / upright

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22
Q

What is the angular magnification?

A

The ratio of the angle subtended by image at the eye to the angle subtended by object at unaided eye ( ß / a )

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23
Q

What would the angular size of the image have to be for an object to be magnified ?

A

It would have to be greater than the angular size of the object ( unaided )

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24
Q

How can you work out the magnification using the focal lengths of a telescope and what adjustment must it be in?

A

Fo / Fe ( focal length of the objective / eyepiece )

Must be in normal adjustment with an angle less than 10 degrees

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25
When is a refractor in normal adjustment ?
- lenses are arranged so the distance between is the sum of the focal lengths ( fo +fe ) - fo > fe
26
What are the two types of telescopes ?
Optical and non optical
27
What is an optical telescope?
Telescopes which use visible light to produce images
28
What is a non optical telescope?
Telescopes that uses the non - visible parts of the Em spectrum to produce images
29
What are the two types of optical telescopes ?
- refracting telescopes and reflecting telescopes
30
What is the difference between refracting telescopes and reflecting telescopes ?
Refracting telescopes produces images when radiation refracts through the glass whereas reflecting telescopes produces images when radiation is reflected of the glass. Refracting telescopes uses lenses where as reflecting telescopes uses two mirrors to focus the light to magnify the object.
31
What is an objective lens ?
A converging lens which produces a real image of a very distant object within the telescope.
32
What is an eyepiece lens ?
A converging lens that acts on the real image produced by the objective lens forming a magnified virtual image
33
What is angular size ?
It is the apparent size that an object appears depending on the actual size and the distance from the observer. Height / distance ( S = r@ )
34
What type of aberration is produced by refracting telescopes ?
Chromatic and spherical aberration
35
What type of aberration is produced by reflecting telescopes ?
Spherical aberration
36
What type of reflecting surface does a concave mirror have ?
The reflecting surface that bulges inside
37
What type of reflecting surface does a convex mirror have ?
A reflecting surface that bulges outside
38
What is chromatic aberration ?
When the edge of a convex lens acts as a prism and split white light into different wavelengths - dispersion of the light passing through - different wavelengths are diffracted by different amounts
39
What is the resolving power of a telescope ?
Measure of how much detail is visible
40
What does the resolving power of a telescope depend on ?
The ‘minimum angular resolution ’ - the smallest angular separation at which the instrument can distinguish two points L.
41
What are problems with refracting telescopes ?
- chromatic abrasion ( spread of ŷ ) - bubbles/ impurities in the glass absorbs some of light ( faint objects aren’t seen ) - large lenses of good quality ( difficult and expensive to produce ) - for a large magnification , objective lens has to have a very long focal length ( long telescope - large and expensive building to house them )
42
What is spherical aberration in reflecting telescopes ?
If the shape of the mirror isn’t quite parabolic , parallel rays reflecting off different parts of the mirror won’t converge at the same point on the optical axis
43
What is the Hipparcos scale ?
A scale which defines the dimmest category of visible stars to have an absolute magnitude of 6 and the brightest category of visible starts to have an absolute magnitude of 1
44
What is luminosity ?
The total amount of energy emitted by a star every second
45
What is the apparent magnitude (m) of a star ?
How bright a star appears compared to others in earth using the hipparcos scale
46
What is the luminosity measured in ?
Watts or joules per sec
47
What is the absolute magnitude of a star ?
How bright a star would appear to be if it were 10 pc from earth
48
What is a light year (ly ) ?
The distance that light travels in one year
49
What is an astronomical unit ( au ) ?
The average distance between the earth and the sun
50
What is the difference between two orders of magnitude ?
2.51 - m = 1 star is 100 times greater than an m=6 star
51
What is a parsec ?
The distance from earth at which a star would have a heliocentric prallax angle of one arcsecond
52
What is the relation ship between the absolute and apparent magnitude ?
m-M = 5log 10 d/10 M- absolute magnitude m - apparent magnitude
53
What is a factor that increases the chromatic aberration ?
The curvature of the lens
54
What is the collecting power ?
The amount of light a lens collects and collecting power is equal to the square of the objective diameter
55
What is a parallax angle ?
Defined as the angle subtended to the star by the line between the sun and the earth
56
What is intensity ?
The energy per second per unit surface area
57
What is a black body ?
- body that is a perfect absorber of radiation ( absorbs all radiation incident on it at all wavelengths ) therefore emitting a continuous spectrum of wavelengths
58
What is Erin’s displacement law ?
- the wavelength at peak intensity , ŷ max is inversely propoproportional to the absolute temperature T of the objects in kelvin
59
What are balmer lines ?
- hydrogen atoms in n = 2 state exists in hot enough stars - such atoms can absorb visible photons at certain wavelengths hence producing absorption lines in continuous spectrum of light from the photosphere
60
How to memorise the class system ?
Oh be a fine girl kiss me ( O B A F G K M )
61
What class stars are blue in colour ?
O b and partly a
62
What class stars are white in colour ?
- a and f and partly g
63
What class stress are yellow in colour ?
- g
64
What class stars are orange in colour
K
65
What class stars are red in colour ?
M
66
What is the temperature range of a o class star ?
25000 - 50000
67
What is the temperature range of a B class star ?
11k - 25 k
68
What is the temperature range of a A class star ?
7.5k - 11k
69
What is the temperature range of a F class star ?
6k - 7.5 k
70
What is the temperature range of a G class star ?
5k - 6k
71
What is the temperature range of a K class star ?
3.5 k - 5 k
72
What is the temperature range of a M class star ?
Under 3500
73
What are the most prominent absorbtion lines of a class o star ?
He+ , He , H
74
What are the most prominent absorbtion lines of a class B star ?
He , H
75
What are the most prominent absorbtion lines of a class A star ?
H , ionised metals
76
What are the most prominent absorbtion lines of a class F star ?
Ionised metals
77
What are the most prominent absorbtion lines of a class G star ?
Ionised ant neutral metals
78
What are the most prominent absorbtion lines of a class K star ?
Neutral metals
79
What are the most prominent absorbtion lines of a class G star ?
Neutral metals , Titanium oxide

Aqa Physics (16 decks)

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