Chapter 6.1-6,2

Question 1

Telescopes

Answer 1

The basic tool of astronomers. Working over the entire range from gamma rays to radio waves, astronomical telescopes collect and concentrate electromagnetic radiation from celestial objects.

Question 2

Resolution

Answer 2

How close two points can be to each other before we can no longer distinguish them.

Question 3

Refracting Telescopes

Answer 3

A telescope that uses objective lenses to collect and focus incoming electromagnetic radiation to form an image.

Question 4

Reflecting Telescopes

Answer 4

A telescope that uses mirrors to collect and focus incoming electromagnetic radiation to form an image in their focal planes the size of a reflecting telescope is defined by the diameter of the primary mirror.

Question 5

Aperture

Answer 5

The clear diameter of a telescopes objective lens or primary mirror.

Question 6

Refraction

Answer 6

The redirection or bending of a beam of light when it crosses the boundary between two mediums having different refractive indices

Question 7

Objective Lens

Answer 7

The primary element in a telescope or camera that produces an image of an object

Question 8

Focal Plane

Answer 8

The plane, perpendicular to the optical axis of a lens or morrow, on which an image is formed.

Question 9

Focal Length

Answer 9

The optical distance between a telescope’s objective lens or primary mirror and the pane on which the light from a distant object is focused.

Question 10

Eyepiece

Answer 10

The lens that is closest to the eye in a telescope. Changing the eyepiece will change the magnification of the image in the telescope.

Question 11

Chromatic Aberration

Answer 11

A detrimental property of a lens in which rays of different wavelengths are brought to different focal distances form the lens.

Question 12

Dispersion

Answer 12

The separation of rays of light into their component wavelengths

Question 13

Compound lens

Answer 13

A lens made up of two or more elements with different refractive indices, the purpose of which is to minimize chromatic aberration.

Question 14

Reflection

Answer 14

The direction of a beam of light that strikes but does not cross the surface between two media having different refractive indices.

Question 15

Diffraction

Answer 15

The spreading of a wave after it passes through an opening or beyond the edge of an object.

Question 16

Diffraction limit

Answer 16

The limit of a telescope’s angular resolution caused by diffraction.

Question 17

Astronomical Seeing

Answer 17

A measurement of the degree to which Earth’s atmosphere degrades the resolution of a telescope’s view of astronomical objects

Question 18

Adaptive Optics

Answer 18

Electro-Optical Systems that largely compensate for image distortion caused by the earth’s atmosphere.

Question 19

Arcsecond

Answer 19

1/3600 of a degree of arc.

Question 20

Magnification=-

Answer 20

Telescope focal length/eyepiece focal length.

Question 21

What are the limitations of a refraction telescope?

Answer 21

1) Physical size limits due to the weight of the lens.
2) Chromatic Aberration
3) Need a large focal length to produce a large image.

Question 22

Who made the first reflection telescope?

Answer 22

Sir Isaac Newton. It used a copper primary mirror and a secondary mirror angled at 45 degrees. The secondary mirror angled the light towards the eyepiece.

Question 23

What makes a good location for an observatory?

Answer 23

1) High. 2) Dry. 3) Dark.

Question 24

Integration Time

Answer 24

Time interval during which the eye can add up photons. Approximately 30 ms.

Question 25

Quantum efficiency

Answer 25

Determines how many responses occur for each photon received. For the human eye 10 photons must strike a cone within 100 ms to activate a single response. So our eyes have 10 percent efficiency.

Question 26

How were early astronomers limited by the human eye?

Answer 26

Because of the integration time and quantum efficiency of the eye. Even large telescopes created images which were very faint and hard to discern using the human eye.alone?

Question 27

Photographic Plates

Answer 27

Used by astronomers. Had 1-3 percent efficiency and used long esposure times to capture an image.

Question 28

Charged Coupled Device

Answer 28

Created by bell laboratories. Linear capturing devices which electronically record images. Efficiency of up to 80 percent at some wavelengths. Photons strike pixels which creates small electrical charges within the silicon.

Question 29

Spectroscopy

Answer 29

The study of an objects spectrum

Question 30

Spectrographs

Answer 30

Instruments that take the spectrum of an object and record it.

Question 31

Diffraction Grating

Answer 31

Used in modern electrocardiographs. Uses engraved closely spaced lines in glass to disperse incoming light into its constituent wavelengths.

Question 32

What are the three most important elements of a telescope?

Answer 32

1) Light gathering power.
2) Resolution
3) Magnification

Question 33

Focus

Answer 33

Where the light comes together in a telescope to produce an image.

Question 34

Spherical Abbe-ration

Answer 34

Light through a lens come into focus at different points.

Question 35

Angular Resolution

Answer 35

Separation of objects in terms of angle. wavelength/diameter of telescope.

Question 36

Light Gathering Power

Answer 36

pie/5 (D^2)