Astro Exam Two
The spectrum of sunlight, when spread out by a spectrograph, has what characteristics appearance?
continuous band of color, crossed by innumerable dark absorption lines
The motions of large portions of Earth's surface, the plates, are caused by
convective flow of material in earths interior
In a simple atom, the electrons making transition between the outermost energy levels and the inntermost energy levels give rise to photos with the
highest energies
What evidence do we have that the sun contains the element iron?
solar spectra show absorption in spectral lines that are characteristic of iron are unique to it
What is the basic structure of Earth's interior?
solid iron inner core, molten iron outer core, rocky mantle, lighter rocky crust
Atoms in a thin, hot gas (such as a neon advertising sign), according to Kirchhoff's laws, emit light at
specific wavelengths or color in a pattern that depends on the element
The chemical makeup of a star's surface is usually inferred by
spectroscopy of the light emitted by the star
What parameters does a photon of blue light NOT differ from a photon of yellow light, in a vacuum?
speed
A spectrograph is a scientific instrument that
spreads out light from a source into its component colors or spectrum
Sometimes high tides are higher than at other times. What name is given to the highest high tides?
spring tides
When do spring tides occur?
whenever the earth, the moon and the sun form a straight line, regardless of which side of earth the moon is on (i.e., at the times of full and new moon)
When do neap tides occur?
whenever the earth-moon line makes a 90 degree angle to the earth-sun line
Sometimes high tides are lower than at other times. What name is given to the lowest high tides?
neap tides
The major constituents of Earth's atmosphere are
77% nitrogen and 21% oxygen
What was the first spacecraft to land human beings on the moon?
Apollo 11
The detector that in many instances has replaced the photographic plate for astronomical photography is the
CCD (charged-coupled device)
The idea that light consists of photons, bundles of pure energy, was first proposed by
Einstein
Who was the first astronomer to build and use a telescope to observe the night sky?
Galileo
Who developed the first reflecting astronomical telescope?
Isaac Newton
Most surface rocks on Earth are younger than a few million years old, whereas ages of lunar rock have been measured in billions of years. Why?
Much of earths surface is continually recycled (created and subducted) by the underlying mantle because of plate tectonic activity; the process does not occur on the moon
What theory about the origin of the Moon is now believed to be correct?
an object about the size of mars crashed into earth, and debris from the collision formed the moon
To a physicist, a blackbody is defined as an object that
absorbs all radiation that falls on it
One technique that astronomers are now using to increase the amount of detail that can be recorded with telescopes is
adaptive optics, were the tilt and shape of mirrors in the telescope are changed many times per second to compensate for atmospheric turbulence
The lunar maria appear smooth because they are
ancient lava flows that occurred soon after the end of an early period of intense bombardment and that have had relatively few impacts since then
The light-gathering power of a telescope depends directly on the
area of its primary mirror or lens
What is a CCD (charged-coupled device)?
array of small light-sensitive elements that can be used in place of photographic film to obtain and store a picture
The hot, dense gas existing on the sun emits energy
at all wavelengths, with a peak at one particular wavelength (color)
What actually moves around the sun along the path we usually call Earth's orbit?
barycenter
The type of rock of which the lunar maria are composed is
basalt
Refraction is the
bending of light as it enters a dense but transparent material at an angle to the perpendicular to the surface of the material
Visible light occupies what position in the electromagnetic spectrum?
between infrared and ultraviolet
Pieces of metal are heated by varying amounts in flame. The hottest of the pieces will be one that shows most prominently what color?
blue
What is the barycenter?
center of mass of the earth-moon system
When a rod of metal is heated intensely, its predominant color will
change from red through orange to white and then to blue
The source of the aurora (northern/southern lights) on Earth is
charged particles trapped by earths magnetic field interacting with the atmosphere
The major reason astronomers seek funds to build larger telescopes is to
collect more light from distant objects
The great mountain ranges of Earth have been produced by
collisions between tectonic plates
A Cassegrain reflecting telescope is constructed using a
concave primary mirror followed by a smaller convex secondary mirror that reflects light back through a hole in the primary mirror
In 1801, Thomas Young performed a crucial experiment on the nature of light when he
demonstrated that wave nature of light by passing light through two slits and obtaining a pattern of bright and dark bands on a screen that he correctly interpreted as interference between the two light beams
In 1670, Isaac Newton performed a crucial experiment on the nature of light when he
demonstrated that white light was made up of colors that could be split by a prism and that these colors were not produced by the glass through which light passed
What characteristics of an astronomical telescope is the most important for determining the angular resolution?
diameter of the objective lens or mirror
What item is considered to be the best one to use in a spectrograph to disperse light into its spectrum of colors?
diffraction grating
Our present understanding of the nature of light is that it
displays behavior of both waves and particles
Billions of years ago, Earth's atmosphere was composed primarily of carbon dioxide. What happened to much of this carbon dioxide?
dissolved into earths oceans
Describe the dynamics of the Earth-Moon system
earths rotation is slowing down, whereas the moon is moving slowly outward away from earth
Electromagnetic radiation moving through space with the speed of light consists of oscillating
electric and magnetic fields, always inseparable, always have the same frequency and wavelength and traveling in the same direction
The magnetic field of Earth is caused by
electric currents flowing in the molten core
All forms of light have what property in common?
electromagnetic radiation
The specific colors of light emitted by an atom in a hot, thin gas (e.g., in a neon tube, a fluorescent bulb, or a gas cloud in space) are caused by
electrons jumping to lower energy levels, losing energy as they do so
What is believed to be the composition of Earth's core?
essentially pure iron
The highest tides on Earth's oceans occur at
full or new moon
What type of electromagnetic radiation has the shortest wavelength?
gamma rays
What kinds of large-scale changes have occurred on the Moon in the last billion years?
gentle sculpting of the landscape by constant meteoroid impact
Violet light differs from red light in that it
has a shorter wavelength than red light
Some possible evidence for water has recently been discovered on the Moon in the form of
ice in deep craters near the north pole, perpetually shaded from sunlight
What is the central idea of the theory of the origin of the tilt in Earth's rotation axis?
impact of the mars-sized body as it ejected the material that formed the moon
what is the origin of the majority of lunar craters?
impacts by meteoric material
Auroral displays are most often seen
in circular regions around the north and south geomagnetic poles
Where are Earth's Van Allen radiation belts located?
in the magnetosphere
If you want to design a device that will detect animals at night by the radiation they give off, even if the night is totally dark, to what wavelength range should you make the device sensitive?
infrared
An atom in which one or more electrons has been removed is known as an
ion
The magnetic field of Earth
is related to its rotation around its axis
A radio telescope
is very similar to a reflecting optical telescope
what is a mare on the Moon?
large area of darker material on the lunar surface
What would be perhaps the most striking feature that a visiting traveler from outer space would notice on approaching Earth, having examined the rest the solar system?
large quantity of liquid water on the surface
What is the lunar regolith?
layer of fine powder covering the lunar surface
Ozone is gas consisting of
molecules containing three oxygen atoms
The star Vega has a higher surface temperature than the sun. Then with IR indicating infrared and UV indicating ultraviolet, Vega emits___IR and ____ UV flux than the sun.
more;more
When a ray of light strikes a smooth mirror surface at an angle to the perpendicular, the ray is reflected
on the "other" side of the perpendicular but at the same angle as the incoming ray
The prime focus of a reflecting telescope is reached by light after
one reflection
Photosynthesis in plants on Earth maintains a balance between what two atmospheric gases?
oxygen and carbon dioxide
Ozone in the stratosphere performs an important task the protects life on Earth. What is it?
ozone absorbs much of the dangerous solar ultraviolet light
Craters are not apparent of Earth at the present time in the abundance seen on the Moon because
pate tectonics has returned crater surface layers into earths interior, and weathering has obliterated the more recent craters
What type of electromagnetic radiation has the longest wavelength?
radio waves
Earth's magnetosphere is the
region beyond earths atmosphere where earths magnetic field protects us from the solar wind
What is the name of a long, winding crack in a lunar mare?
rille
The waves the geologists and geophysicists use to probe the inside of Earth are
seismic waves
What wave effect is NOT electromagnetic in nature?
seismic waves
According to Kichhoff's laws, the continuous spectrum of light from a hot star, after passing through a cool gas cloud,
shows absorption features where light has been absorbed by the atoms of the cool gas
To what does planetary differentiation refer?
sinking of heavier elements toward the center of a planet and the floating of lighter elements toward the surface
How many times have human beings landed on the moon?
six times
It is difficult to improve the angular resolution of optical telescopes located on the surface of the Earth beyond a certain limit because
star images are distorted more by air turbulence than by the telescope optics
We have found that the upper layers of the mantel are "plastic." Why is this important?
the continents are able to float and drift on these layers
Why so the larger craters on the Moon have central peaks?
the crater floor rebounded upward after the initial compression from the impact of an interplanetary rock
If a certain gas is heated and observed through a grating, a bright line spectrum will be seen. If instead a source of continuous spectrum shines through a cooler sample of the same gas, a dark absorption spectrum is observed. How do the positions of the lines in these two spectra compare?
the lines in the two spectra will be at the same frequencies. They will be the same spectra
Why is it that terrestrial planets are thought to have dense iron cores?
the plates were molten early in their life, and the heavy elements sank and lighter materials floated to the surface (planetary differentiation)
All the boundaries of the major interacting tectonic plates on Earth's surface are coincident with
the positions of maximum earthquake occurrence
To observers on Earth, the moon shows
the same side at all times
Earth's magnetic field protects Earth and its inhabitants from
the solar wind, which would otherwise irradiate and damage life forms if not deflected
The mountain ranges on the moon are
the walls of craters caused by impacts of large objects early in the geological history of the moon
What is the one fundamental difference between x rays and radio waves?
the wavelengths of x rays and radio waves are very different
What is the main reason for using several radio telescopes together as an interferometer?
to obtain much better angular resolution of sharpness in the images
In which layer of Earth's atmosphere does weather occur?
troposphere
The moon produces tidal disturbances on the oceans of Earth. In general, there are
two high and two low tides per day
The Mid-Atlantic Ridge in Earth's crust is a region where
two tectonic plates are slowly spreading apart
The San Andreas fault in California is an example of
two tectonic plates sliding past each other
Earth's albedo is the fraction of radiant energy from the sun that Earth re-radiates into space. This number
varies slightly both daily and seasonally
The two ranges of electromagnetic radiation for which the Earth's atmosphere is reasonably transparent are
visible and radio radiation
What is sequence of electromagnetic radiation?
visible light, UV radiation, x rays, gamma rays
the proper motion of a star on other object is measured by
watching the object move compared to the background stars
