Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Physics Aqa > 3.9.1 Telescopes > Flashcards

3.9.1 Telescopes Flashcards

You may prefer our related Brainscape-certified flashcards:
Physics 101 flashcards AP® Physics flashcards
1
Q

What do convex lenses do to incident light?

A

They focus the light

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What are convex lenses also know as ?

A

Converging lenses

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What do concave lenses do to incident light?

A

They spread out light

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is the principle axis?

A

The line passing through the centre of the lens perpendicular to its surface

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is the principle focus for a convex lens?

A

the point where incident rays of light will converge

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is the principle focus for a concave lens?

A

The point where incident rays of light appear to be coming from

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is the focal length?

A

The distance between the principle focus and the centre of the lens

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

The shorter the focal length ….

A

the stronger the lens

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is the real image?

A

The image formed when light rays cross after refraction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is unique about the real image?

A

It can be formed on a screen

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is the virtual image?

A

The image formed on the same side of the lens

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

With regards to the virtual image, what happens to the light rays?

A

They don’t cross

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What can’t be done with the virtual image?

A

It can’t be formed on a screen

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is the lens formula?

A

1/u + 1/v = 1/f

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

In the lens formula, what is u?

A

Distance of the object from the centre of the lens

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

In the lens formula, what is v?

A

Distance of the image from the centre of the lens

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

In the lens formula, what is f?

A

The focal length of the lens

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What is the unit for the power of a lens?

A

Dioptres (D)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What is the power of a lens a measure of?

A

A measure of how closely a lens can focus a beam

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What is the value of the power of a convex lens?

A

Positive

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What is the value of the power of a concave lens?

A

Negative

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Regarding a refracting telescope in normal adjustment, which lens collects light?

A

The objective lens

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Regarding a refracting telescope in normal adjustment, why does the objective lens collect light?

A

To create a real image of a very distant object

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Regarding a refracting telescope in normal adjustment, why does the objective lens have a long focal length?

A

To collect as much light as possible

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

Regarding a refracting telescope in normal adjustment, what does the eyepiece lens do?

A

It magnifies the image produced by the objective lens

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

Regarding a refracting telescope in normal adjustment, why is the eyepiece lens useful?

A

It produces a virtual image at infinity that reduces eyestrain for the observer

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

Normal adjustment for a refracting telescope is the sum of what?

A

The two focal lengths
or fe+fo

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

Regarding a refracting telescope in normal adjustment, principle focus for the two lengths are always where?

A

In the same place

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

What is the equation for angular magnification? (magnifying power)

A

α/β (Larger angle over smaller angle)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

What happens when α and β are both less than 10 degrees?

A

α/β = fo/fe

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

Regarding a Casegrain reflecting telescope, what is the primary mirror?

A

A parabolic/concave objective mirror

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

Regarding a Casegrain reflecting telescope, what is the secondary mirror?

A

A convex mirror

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

Regarding a Casegrain reflecting telescope, where are the principle foci? (2)

A

After the secondary mirror and there is a virtual one behind the mirror

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

Regarding a Casegrain reflecting telescope, what lens is used to focus light?

A

A convex lens

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

What is a merit of reflecting mirrors? (2)

A

They are very thin
They have a coating of aluminium or silver atoms

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

What is an advantage of mirrors having a coating of aluminium or silver atoms?

A

They are smooth, minimising distortion

37
Q

What do reflecting telescopes prevent? (2)

A

Chromatic aberation
Spherical aberation

38
Q

What is chromatic aberation?

A

when red light has a greater focal length than blue light

39
Q

In chromatic aberation, why does red light have a greater focal length than blue light?

A

because blue light is refracted more

40
Q

How can you tell if an image is being effected by chromatic aberation?

A

the images are produced with coloured fringing

41
Q

What is spherical aberation?

A

when rays of light are focused in different positions

42
Q

How does spherical aberation occur?

A

The curvature of the lens or mirror can cause rays of light at the edge to be focused in different positions

43
Q

What types of lenses does spherical aberation effect?

A

Lenses with large diameters

44
Q

How can you tell if an image has been effected by spherical aberation?

A

The image will be blurred or distorted

45
Q

How can spherical aberation be completely avoided?

A

By using parabolic objective mirrors

46
Q

Which is lighter a lens or a mirror?

A

A mirror

47
Q

What are disadvantages of refracting mirrors?

A

Glass must not have defects
Large lenses can bend or distort under their own weight
They’re heavy
They’re not easy to move
Large magnifications require large lenses
Can only be supported from the edges

48
Q

What is an advantage of using reflecting telescopes?

A

Eliminates chromatic or spherical aberation
They’re thin
They’re not heavy
Large ones can be made of smaller ones
They can be supported from behind

49
Q

What are similarities of radio and reflecting telescopes?

A

They focus incoming radiation and focus it
They can be moved to focus on different objects
They both have a parabolic shape

50
Q

What are differences between radio and optical telescopes?

A

Radio telescopes have a very large diameter, to collect radio waves (due to their large wavelength)
Radio telescopes are much cheaper to build
Radio telescopes have to move to focus on objects
Radio experiences a large amount of man-made interference
Radio has a better collecting power
Radio must have a much greater diameter to achieve the same resolving power as optical telescopes

51
Q

What are infrared telescopes made up of?

A

Large concave mirrors focussing radiation onto a detector

52
Q

How must infrared telescopes be kept? (2)

A

Cooled using cryogenic fluids to almost absolute 0
Shielded to prevent thermal contamination

53
Q

What areas of space do infrared telescopes observe?

A

Cooler regions of space

54
Q

Where can infrared telescopes also be stationed?

A

In space and remote controlled from Earth

55
Q

Where must UV positioned?

A

In space

56
Q

Why can’t UV telescopes be positioned on Earth?

A

Because the ozone layer blocks all UV rays less than 300nm

57
Q

What configuration do ultraviolet telescopes use?

A

Cassegrain

58
Q

How do gamma telescopes create images?

A

Don’t use mirrors, use a detector made of pixels

59
Q

What do gamma telescopes observe? (4)

A

Gamma ray bursts
Quasars
Blackholes
Solar flares

60
Q

Where do X-ray telescopes have to be stationed?

A

in space

61
Q

Why do X-ray telescopes have to be stationed in space?

A

Because X-rays are absorbed by the atmosphere

62
Q

What are X-ray telescopes comprised of?

A

A combination of parabolic and hyperbolic mirrors

63
Q

What do X-ray telescopes usually observe? (4)

A

High energy areas of space:
Active galaxies
Blackholes
Neutron stars

64
Q

What is collecting power of a lens/mirror?

A

The ability to collect incident EM radiation

65
Q

What is collecting power inversely proportional to?

A

the area of the objective lens

66
Q

The greater the collecting power…..

A

The brighter the image produced

67
Q

What is resolving power?

A

The ability of a telescopes to produce separate images of close together objects
or a measure of of how much detail you can see

68
Q

What is needed for an image to be resolved?

A

The angle between the straight lines from Earth to each object must be at least the minimum angle resolution

69
Q

According to Rayleigh’s criterion what causes images not to be resolved?

A

If any part of the central maximum of either image falls within the first minimum diffraction

70
Q

What is collecting power proportional to?

A

Diameter squared

71
Q

What does CCD stand for?

A

Charged-coupled devices

72
Q

What is quantum efficiency?

A

the percentage of incident photons which cause an electron to be released

73
Q

What is pixel resolution?

A

The number of pixels used to form an image on a screen

74
Q

Regarding pixel resolution, what can a large amount of small pixels do that a small amount of large pixels can’t?

A

A lot of small pixels can resolve an image more clearly than a small amount of
large pixels.

75
Q

What is spatial resolution?

A

The minimum distance that two objects must be apart in order to be distinguishable

76
Q

What is spatial resolution used to do?

A

Observe small objects

77
Q

What is convenience?

A

How easy images are to form and use

78
Q

What is the quantum efficiency of a CCD?

A

Roughly 80%

79
Q

What is the quantum efficiency of the human eye?

A

4-5%

80
Q

What is the spectral range of a CCD?

A

IR, UV and visible

81
Q

What is the spectral range of the human eye?

A

Only visible

82
Q

What is the pixel resolution of a CCD?

A

Varies but is roughly 50 megapixels

83
Q

What is the pixel resolution of the human eye?

A

roughly 500 mega pixels

84
Q

What is the spatial resolution of a CCD?

A

10 micro metres

85
Q

What is the spatial resolution of the human eye?

A

100 micro metres

86
Q

What is the convenience of a CCD?

A

Needs to be set up but image produced are digital

87
Q

What is the convenience of the human eye?

A

Simpler to use, no need for extra equipment

88
Q

What are CCD’s more useful for?

A

detecting finer details and producing images which can be shared and stored

Physics Aqa (11 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions