Chapter 4: AS 101
What does the word "radiation" mean when used by scientists? Question options: invisible forms of light such as X-rays and radio waves the light emitted by black holes and protostars high-energy particles from nuclear reactors anything that spreads out from a central source
anything that spreads out from a central source
Which of the following sequences of electromagnetic radiation shows the order of increasing energy correctly? Question options: gamma rays, X-rays, infrared, radio visible, ultraviolet, X-rays, gamma rays visible, microwave, radio, infrared infrared, visible, radio, X-rays
visible, ultraviolet, X-rays, gamma rays
When does chromatic aberration occur in a telescope? Question options: when different colours of light do not focus at the same point in a reflecting telescope when different colours of light do not focus at the same point in a refracting telescope when light of different wavelengths gets absorbed by the mirror in a reflecting telescope when light of different wavelengths gets absorbed by the lens in a refracting telescope
when different colours of light do not focus at the same point in a refracting telescope
The Stratospheric Observatory for Infrared Astronomy
- A telescope carried by a Boeing aircraft. - Operates above 99% of the water vapour in the atmosphere. - A telescope that observes at far-infrared wavelengths must be cooled and kept cooled.
Interferometry
- A way to improve resolving power is to connect two or more telescopes in an interferometer (
Telescopes
- Astronomers build optical telescopes to gather light and focus it into sharp images. - This is what a telescope can do: - Light gathering - Resolving - Magnifying power
Wave length
- Electromagnetic radiation exhibits the wave nature - Wavelength - The distance between successive peaks or troughs of a wave. - Commonly measured in nanometres and angstrom.
Kepler's Hall of Fame
Measures brightness of all 100,000 stars once every 30 minutes Can see changes of 100 parts per million or smaller
What is the relationship between colour and wavelength for light? Question options: Wavelength increases from blue light to red light Wavelength decreases from blue light to red light All colours of light have the same wavelength Wavelength depends on intensity, not colour
Wavelength increases from blue light to red light
Which of the following types of electromagnetic radiation has the smallest frequency? Question options: X-rays radio waves visible light infrared radiation
radio waves
How does long-wavelength visible light appear to the average human eye? Question options: invisible green blue red
red
Radian
refers to anything that spread outward from a source, light radiation from a source
What type of telescope is a radio telescope? Question options: reflecting refracting deflecting retracting
reflecting
What type of telescope has a lens as its objective and contains no mirrors? Question options: deflecting reflecting refracting compound
refracting
In which way is a photon of blue light identical to a photon of red light? Question options: energy speed wavelength frequency
speed
large telescopes
prime focus position high in telescope, scondary mirror can reflect light through a hold in primary mirror to cassegrain focus
Spectrographs
- A spectrograph is a device that separates light into a spectrum using a grating
- Imaging Systems and Photometers
- For many decades, astronomers used photographic plates and photometers. - charge-coupled device (CCD) - An electronic device consisting of a large array of light- sensitive elements. - CCD images are digitized (converted to numerical data) and can be stored for later analysis. -measure brightness of individual objects very precisely
Radiation: Information from Space and Light
- Light behaves both as a wave and a particle. - Light can travel through empty space. Unlike light, sound waves need a medium to propagate. - Light is composed of electric and magnetic waves electromagnetic radiation. - The electromagnetic spectrum includes gamma rays, X-rays, ultraviolet radiation, visible light, infrared radiation, microwaves, and radio waves. -does not require a medium -a type of electromagnetic radiation -visible light is only one form
Optical and Radio Observatories
- Light pollution - The illumination of the night sky by waste light from cities and outdoor lighting, which prevents the observation of faint objects. - Telescopes on Earth must move continuously (sidereal tracking) to compensate for Earth's rotation and stay pointed at celestial objects. - An ideal location for a ground based telescope - a mountain top, dry air, away from city lights and human-made radio signals.
The Very large Telescope (VLT)
- Located high in the remote Andes Mountains of northern Chile - Consists of four telescopes
Optical, Infrared, and Submillimetre Telescopes
- Mauna Kea in Hawaii (altitude 4200 m) - The high altitude, low atmospheric moisture, no light pollution, and location near the equator make this mountain one of the best places on Earth to build an observatory
The Chandra X-ray Observatory
- Orbits a third of the way to the Moon.
photon
- Photon: a particle of light -buncle of electromagentic waves -amount of energy photon carries depends on wavelength of light -shorter carry more -visible photons carry little energy -astronomers uses electromeganetic radiation for planets, stars and other celstial objects
Gamma- Ray Telescopes
- The Compton Gamma Ray Observatory - Mapped the entire sky at gamma-ray wavelengths. - The European INTEGRAL satellite - Important in the study of violent eruptions of stars and black holes. - The GLAST (Gamma-Ray Large Area Space Telescope) - Capable of mapping large areas of the sky to high sensitivity
Webb Space Telescope at L(2)
- The L2 point lies on the line through the two large masses, beyond the smaller of the two. Here, the gravitational forces of the two large masses balance the centrifugal effect on a body at L2 - Webb often gets called the replacement for Hubble, but we prefer to call it a successor. After all, Webb is the scientific successor to Hubble; its science goals were motivated by results from Hubble. Hubble's science pushed us to look to longer wavelengths to "go beyond" what Hubble has already done. In particular, more distant objects are more highly redshifted, and their light is pushed from the UV and optical into the near-infrared. Thus observations of these distant objects (like the first galaxies formed in the Universe, for example) requires an infrared telescope
Telescopes and their Light Gathering Power
- The ability of a telescope to collect light - Proportional to the area of the telescope's objective lens - Catching light in a telescope is like catching rain in a bucket - the bigger the bucket , the more rain it catches
Resolving Power
- The ability of the telescope to reveal fine detail. - Diffraction fringe - Because of this, no image detail smaller than the fringe can be seen - The resolving power of a telescope is also affected by: - Optical quality of the telescope - Atmospheric conditions - Seeing : atmospheric conditions on a given night - Twinkling in the stars is produced by turbulence in Earth's Atmosphere
The Largest...
- The largest fully steerable radio telescope is at the National Radio Astronomy Observatory in West Virginia. - The largest single telescope (for now) is the Gran Telescopio Canarias. - The largest radio dish in the world is built into a mountain valley in Arecibo, Puerto Rico.
light
-combination of electric anf
atmospheric windows, what can pass through
-gamma, xray, and some radio are absrobed by atmosphere -water vapour lower abosrbs longer IR -visible, short wavelength IR and some radio waves reach earth surface through this must look through these to see sky from earth surface
- Angstrom (Å) -
1 Å = 10−ϭϬ m
two factors limiting resolving power
1. optical quality 2. atmosophere conditions (cant see to full potential = seeing, steadiness of air conditions)
What is the ratio of the light-gathering power of a 10-metre telescope to that of a 1-metre telescope? Question options: 10 to 1 1 to 10 100 to 1 1 t100
100 to 1
The pupil of the human eye is approximately 0.8 centimeters in diameter when adapted to the dark. What is the ratio of the light-gathering power of a 1.6 meter telescope to that of the human eye? Question options: 2 : 1 20 : 1 400 : 1 40,000 : 1
40,000 : 1
What is the longest wavelength of light that can be seen with the human eye? Question options: 400 nanometres 700 nanometres 7000 nanometres 3×108 m
700 nanometres
Refracting Telescope
: A telescope that forms images by bending (refracting) light with a lens, curved piece of glass, on a reflective surface, forms an image by bouncing light, primary mirror, form a coloured ring around planets
Reflecting Telescope
: a telescope that forms images by reflecting light with a mirror, a lens bends the light as it passes through and brings into focus (the image), cheaper
Telescopes Adaptive Optics
A computer- controlled optical system in an astronomical telescope used to partially correct for seeing.
The Kepler telescope -
A space telescope designed to look for Earth-like (and possibly habitable) planets around other stars
How do photons of blue light differ from photons of red light? Question options: Blue light photons have more energy than photons of red light Blue light photons have a lower frequency than photons of red light Blue light photons have a longer wavelength than photons of red light Blue light photons travel faster than photons of red light
Blue light photons have more energy than photons of red light
An astronomer takes two pictures of the same object using the Hubble Space Telescope. One picture is taken with red light and one with blue light. Which one would you expect to show finer details? Question options: Blue light will show finer details Red light will show finer details Both should be the same The amount of detail depends on the distance to the object
Blue light will show finer details
What is a similarity between radio and optical telescopes? Question options: Both can observe from the Earth's surface Both are usually located on mountaintops Both are usually made as refracting telescopes Both can detect radiation with charge-coupled devices
Both can observe from the Earth's surface
Why can't a telescope image be magnified to show any level of detail? Question options: Diffraction limits the amount of detail that is visible Telescopes only view a small region of the sky Magnification depends on focal length Resolving power depends on wavelength
Diffraction limits the amount of detail that is visible
How does the energy of a photon relate to the other properties of light? Question options: Energy is directly proportional to the wavelength of the light Energy is inversely proportional to the wavelength of the light Energy depends only on the speed of the light Energy is inversely proportional to the frequency of the light
Energy is inversely proportional to the wavelength of the light
What can be done to improve the resolving power of ground-based optical telescopes? Question options: Use them at longer wavelengths Equip them with an adaptive optics system Change them from reflectors to refractors Increase their focal length
Equip them with an adaptive optics system
300 nanometer light has a lower frequency than 500 nanometer light Question options: True False
False
X-rays easily penetrate the Earth's atmosphere and reach the ground from space Question options: True False
False
How is the resolving power of a telescope defined? Question options: It is a measure of the minimum angular separation that can be seen with the telescope It is a measure of the amount of light that the telescope can gather in one second It is the separation between the objective and the imag It is a measure of how blurry objects appear in the telescope
It is a measure of the minimum angular separation that can be seen with the telescope
What is the purpose of interferometry? Question options: It is used to improve the resolving power of telescopes It is used to decrease the chromatic aberration of a telescope It is used to make large X-ray and ultraviolet telescopes It allows radio telescopes to be within a few hundred feet of each other
It is used to improve the resolving power of telescopes
What is the main reason for building large optical telescopes? Question options: It's the best way to see through clouds and other light-absorbers in the atmosphere It's the best way to collect as much light as possible from faint objects It's the best way to nullify the blurring effects of the Earth's atmosphere and thus produce higher resolution images It's the best way to magnify objects and make them brighter
It's the best way to collect as much light as possible from faint objects
Question options: Its light-gathering power and resolving power both increase Its light-gathering power increases and its resolving power decreases Its light-gathering power decreases and its resolving power increases Its light-gathering power and resolving power both decrease
Its light-gathering power and resolving power both increase
The Herschel Space Observatory -
Observes from behind a sunscreen.
Which of the following best explains the concept of atmospheric windows? Question options: Holes in the Earth's atmosphere allow ultraviolet radiation to reach the North and South poles X-ray radiation from space can see through the atmosphere to observe activities on the ground Only certain wavelengths of electromagnetic radiation from space reach the Earth's surface The Earth's atmosphere can be "closed" or "open" to electromagnetic radiation, depending on the weather
Only certain wavelengths of electromagnetic radiation from space reach the Earth's surface
Why do astronomers build radio telescopes? Question options: Radio waves give a different view of the universe Radio waves from space reach the Earth's surface Radio telescopes can detect signals from aliens Radio telescopes can be much larger than optical telescopes
Radio waves give a different view of the universe
Herschel Telescope
The Herschel Space Observatory was a space observatory built and operated by the European Space Agency (ESA). It was active sensitive to the far infrared and submillimetre wavelengths (55-672 μm). he observatory was carried into orbit in May 2009, reaching the second Lagrangian point (L2) of the Earth- Sun system, 1,500,000 kilometres from Earth, about two months later.
Which of the following statements about the Earth's atmosphere is true? Question options: The atmosphere is transparent to most radio waves The atmosphere is opaque to most radio waves The atmosphere is transparent to X-rays The atmosphere is opaque to most visible wavelengths
The atmosphere is transparent to most radio waves
How is the objective of most radio telescopes similar to the objective of a reflecting optical telescope? Question options: They are both bowl-shaped (concave) They are both hill-shaped (convex) They are typically the same size They are both made of metal
They are both bowl-shaped (concave
A(n)______________________is used to measure the brightness and colour of stars
___photometer__
What is a photon? Question options: a type of electromagnetic radiation a particle within the atmospheric window a particle produced when light interacts with vacuum a particle of light
a particle of light
- Eyepiece:
a short focal length lens used to enlarge the image in a telescope, to see image
What type of telescope is most likely to suffer from chromatic aberration and have a low light-gathering power? Question options: a small diameter reflecting telescope a large diameter reflecting telescope a small diameter refracting telescope a large diameter refracting telescope
a small diameter refracting telescope
Which of the following has the most light-gathering power? Question options: a telescope of 5 centimeters diameter and focal length of 50 centimeters a telescope of 6 centimeters diameter and focal length of 100 centimeters a telescope of 2 centimeters diameter and focal length of 100 centimeters a telescope of 3 centimeters diameter and focal length of 75 centimeters
a telescope of 6 centimeters diameter and focal length of 100 centimeters
magnifying power
ability to see a large imagem combined with focal length of primary mirror or lens divided by focal length of eye piece, higher magnification doesnt mean more detail, limited by other things -diameter of telescope is most important
Which form of electromagnetic radiation travels fastest? Question options: gamma rays radio waves all electromagnetic radiation travels at the same speed the speed of radiation depends on the brightness of the source
all electromagnetic radiation travels at the same speed
Diffraction fringe -
blurred fringe surrounding any image, caused by the wave properties of light, smaller issues in large -depends on size of images, depends on wavelength -long = more diffraction image -improved using an interferometer,
adaptive optics
compensate for distortions
power of telescope is dependent on
diameter
You point your backyard reflecting telescope at the star Vega. Where does Vega's light go? Question options: from the primary mirror, to the secondary mirror, to the eyepiece from the primary mirror to the eyepiece through the primary lens, to the secondary mirror, to the eyepiece through the primary lens, through the secondary lens, to the eyepiece
from the primary mirror, to the secondary mirror, to the eyepiece
Which of the following types of electromagnetic radiation has the greatest energy per photon? Question options: X-rays radio waves gamma rays infrared radiation
gamma rays
Which of the following types of light has wavelengths that are shorter than the wavelengths of visible light? Question options: gamma rays radio waves infrared radiation microwaves
gamma rays
optical telescopes
gather light but also radio radiation (radio telescope), radio waves from celestial objects
Which of the following types of light has wavelengths that are longer than the wavelengths of visible light? Question options: gamma rays ultraviolet infrared X-rays
infrared
Which of the following types of electromagnetic radiation has the lowest energy per photon? Question options: X-rays ultraviolet light gamma rays infrared radiation
infrared radiation
Which of the following types of electromagnetic radiation is absorbed by water lower in the Earth's atmosphere, but can be detected by telescopes that are on mountaintops or are carried by aircraft? Question options: infrared radiation ultraviolet radiation radio wave radiation X-ray radiation
infrared radiation
What does a nanometre measure? Question options: frequency energy mass length
length
What type of primary is found in a reflecting telescope? Question options: prism mirror lens diffraction grating
mirror
Nanometre (nm) -
one-billionth of a metre (10-9 m)
What statement below best describes the refraction of light? Question options: the absorption of light as it travels though a dense, transparent material the spreading out of white light according to wavelength the change in direction of a light ray as it passes to a medium of different optical density the change in direction of a ray of light as it reflects off a surfac
the change in direction of a light ray as it passes to a medium of different optical density
Which property of a telescope determines its light-gathering power? Question options: the focal length of the objective the focal length of the eyepiece the diameter of the objective the length of the telescope tube
the diameter of the objective
What is the light-gathering power of a telescope directly proportional to? Question options: the diameter of the primary mirror or lens the focal length of the primary mirror or lens the length of the telescope tube the diameter of the eyepiece
the diameter of the primary mirror or lens
Which of the following statements best describes the wavelength of a wave? Question options: the measure of how strong the wave is the distance between two adjacent peaks of the wave the measure of how fast the wave is the distance between a peak of the wave and the next trough
the distance between two adjacent peaks of the wave
- Focal Length:
the distance from that lens or mirror to the point where it focuses parallel rays of light., distant from lens or mirror to image, forms from a distant object
- Primary Lens:
the largest lens (refracting) or mirror (reflecting)
sidereal tracking
track stars in sky
sound
type of wave that has air pressure distubances, from source to ear, requires liquid, solid or gas to carry
Electromagnetic spectrum
types of electromagnetic radiation arranged in order of increasing wavelength rainbow is a spectrum of visible light (400nm -700nm) -beyond red is infared radiation (700-1nm) -wavelengths have a longer wavelength that IR -shorter than violet = ultraviolet (UV) -longest = infared radiation -smallest= microwave
Which of the following types of electromagnetic radiation is absorbed by ozone in the Earth's atmosphere? Question options: infrared radiation ultraviolet radiation X-ray radiation visible light
ultraviolet radiation
small telescope
use other such newtonian, schmidit cassegrain to foucs -doesnt work for larger
