ASTRO 101 CH. 5 HMW
reflecting telescopes
-the hubble space telescope -most commonly used by professional astronomers today -world's largest telescope
A planet with twice Earth's mass orbiting at a distance of 1 AU from a star with the same mass as the Sun.
1 year
According to the law of universal gravitation, what would happen to Earth if the Sun were somehow replaced by a black hole of the same mass?
Earth's orbit would not change.
Radio waves are:
a form of light.
Suppose Star A and Star B are both moving away from you, but Star A is moving faster. Then the spectrum of Star A will show
a greater redshift than the spectrum of Star A will show
the atom in which the electron leaves (the atom is ionized) corresponds with the highest-energy photon
and the atom with the shortest arrow indicates the case where the absorbed photon had the lowest energy.
The absorption line spectrum shows what we see when we look at a hot light source (such as a star or light bulb) directly behind a cooler cloud of gas. Suppose instead that we are looking at the gas cloud but the light source is off to the side instead of directly behind it. In that case, the spectrum would __________.
be an emission spectrum
If a star is moving away from you, absorption lines that are in the infrared portion of the electromagnetic spectrum will be
shifted such that they are farther from the visible portion of the spectrum
The higher the energy of a photon, the ________ its wavelength.
shorter
when you listen to the radio you are hearing
sound not light
suppose you go outside and look at three stars. star a is blue, star b is white, star c is red. which star is the hottest and which star is the coldest?
star a is the hottest and star c is the coldest
Which telescope has a better (smaller) angular resolution: a 2 meter telescope observing visible light (wavelength 5.0x10^-7m) or a 10 meter radio telescope observing radio waves (wavelength 2.1x10^-2m)?
the optical telescope
In space or air, the speed of light is __________.
the same for light of all wavelengths
Which of the following statements is not a valid advantage for having a telescope in orbit above our atmosphere?
the telescope is closer to the astronomical objects
Suppose that two objects collide. Which of the following things is NOT the same both before and after the collision?
the total temperature of the objects
If the emission lines in the spectrum of one object are more strongly blue shifted than those from a second object, then the first object is moving
towards us faster than the second object
At a supermarket in France, the price of apples is 2.50 euros per kilogram. Suppose the exchange rate is 1 euro = $1.35. What is the price of the apples in dollars per pound? Recall that 1kilogram=2.205pounds.
$1.53/pound
China mandates that new cars have an average fuel efficiency of 17.9 kilometers per liter. Given that 1 mile is about 1.6 kilometers, and 1 gallon is about 3.8 liters, choose the equation that gives the equivalent fuel efficiency in miles per gallon.
(17.9 km/L)×(1 mile/1.6 km)×(3.8 L/1 gal)
The many more lines in the yellow and red parts of the spectrum are what make "pure" neon lights look red or orange.
(When you see "neon lights" glowing with other colors (besides reddish-orange), it is generally because they contain additional elements (besides neon) making them glow.)
refracting telescopes
-Galileo's telescopes -the world's largest is 1 meter in diameter -incoming light passes through glass -very large telescopes become top heavy
Which of the following statements is NOT one of Newton's Laws of Motion? - In the absence of a net force acting upon it, an object moves with constant velocity. -For any force, there always is an equal and opposite reaction force. -What goes up must come down. -The rate of change of momentum of an object is equal to the net force applied to the object.
-What goes up must come down.
Convert a mass of 1012 micrograms to kilograms.
1000 kilograms
How much greater is the light collecting area of a 4 meter telescope than that of a 1 meter telescope?
16 times greater
The acceleration of gravity on Mars is about 3.7 meters per second squared. Suppose a rock falls from a tall cliff on Mars. Which of the following equations indicates how fast the rock will be falling after 8 seconds?
3.7 m/s^2 ×8 s
The acceleration of gravity on Earth is approximately 10 m/s2 (more precisely, 9.8 m/s2). If you drop a rock from a tall building, about how fast will it be falling after 3 seconds?
30m/s
If you assume that there are exactly 365 days in a year, how many seconds are there in one year? Give your answer to the nearest 1000 seconds.
31,536,000 seconds
Consider the total amount of light collected by a 4 meter telescope observing a star for 10 minutes. If you wanted to collect the same amount of light with a 2 meter telescope, how long would you need to observe?
40 minutes
if an atom contained only four energy levels, how many possible different emission lines could it emit?
6
A planet with the same mass as Earth orbiting at a distance of 1 AU from a star with four times the Sun's mass
6 months
True or False? All forms of light easily travel through Earth's atmosphere.
False
True or False? If we used a filter to block out the reddish-orange color of the neon "OPEN" sign, it would appear absolutely dark.
False
Because the cloud absorbs light from the hot source, conservation of energy demands that it must re-emit light with the same total amount of energy.
However, this re-emitted light is sent in all directions, not just along the direction from which it originally came. Therefore, if we view the cloud from a location from which we can see only the light that the cloud itself emits, we will see an emission line spectrum.
While visible light can be observed from the ground, ultraviolet light can be easily observed only from space.
Indeed, the capability of observing ultraviolet light is a major advantage of the Hubble Space Telescope over larger ground-based telescopes.
Why is Newton's version of Kepler's third law so useful to astronomers?
It can be used to determine the masses of many distant objects.
Why is a sunflower yellow?
It reflects yellow light.
The Sun can simplistically be pictured as a hot interior light source surrounded by a thin, cooler layer of gas (the Sun's photosphere).
The interior produces a continuous spectrum, while the overlying gas acts like a cloud to produce absorption lines.
Both visible light and radio waves pass almost freely through Earth's atmosphere, and therefore are easily observed with ground-based telescopes.
The only other light that can be observed with ground-based telescopes is infrared, but it can be detected only at high altitudes (such as mountaintops) and even then only in selected portions of the infrared spectrum.
As your answer correctly shows, the emitted photon must have exactly the same amount of energy that the electron loses in moving from the higher to the lower energy level.
Therefore the ranking of the photon energies must be in the same order as the amounts of energy lost by the electrons, and longer arrows mean greater changes in energy.
True or False? During the day, we see most objects because of the reflected sunlight that enters our eyes.
True
I make it a habit to be weightless for at least a fraction of a second every day True/False
True - This statement makes sense because you are weightless any time you are not in contact with the floor or ground, which can happen simply by jumping at least once every day.
Which of the following types of light cannot be studied with telescopes on the ground?
X rays
Recall that one of the laws of thermal radiation states that a higher-temperature object emits photons with higher average energy (Wien's law). This law is illustrated by the fact that for a higher temperature object, the graph peaks at __________.
a shorter wavelength Wien's law states that the thermal radiation from a hotter object peaks at a shorter wavelength.
which object emits more infrared radiation?
a star that is the same size as the sun but 5 times hotter
The Hubble Space Telescope obtains higher-resolution images than most ground-based telescopes because it is:
above Earth's atmosphere.
What type of visible light spectrum does the Sun produce?
an absorption line spectrum
If a star is moving away from you the absorption lines in it spectrum will
be redshifted (have wavelengths longer than those of an identical stationary star)
The set of spectral lines that we see in a star's spectrum depends on the star's:
chemical composition
A star whose spectrum peaks in the infrared is:
cooler than our Sun
Reflecting telescopes gather and focus light with a __________.
curved mirror
If our eyes were sensitive only to X rays, the world would appear __________.
dark because X-ray light does not reach Earth's surface
When a spinning ice skater pulls in his arms, he spins faster because _________.
his angular momentum must be conserved, so reducing his radius must increase his speed of rotation
For an object's radial speed (toward or away from us) to be measured with a Doppler shift, what must we be able to see in the object's spectrum?
either absorption or emission lines
Because X rays from the Sun do not reach Earth's surface
eyes that were sensitive only to X rays would have nothing to see.
How much greater is the light-collecting area of a 6-meter telescope than a 3-meter telescope?
four times
Doppler shift measures motion only towards or aways from you. That means the true speed of an object (including both motion towards or away from us and motion across our line of sight) is likely to be
greater than the speed measured by the Doppler shift
An electron can be ejected from an atom if it absorbs a photon that __________.
has more energy than is needed to raise the electron to the highest energy level
Compared to red light, blue light has higher frequency and
higher energy and shorter wavelength.
If a hot gas cloud is moving towards us, the frequency of the emission lines will be
higher than those of a stationary gas cloud
If you had only one telescope and wanted to take both visible-light and ultraviolet pictures of stars, where should you locate your telescope?
in space
After the atoms in a gas cloud absorb photons of specific wavelengths (the wavelengths of the absorption lines) from a light bulb or star, the energy from these photons __________.
is returned to space when the atoms re-emit photons with the same total amount of energy, but in random directions
Compared to an atom as a whole, an atomic nucleus:
is very tiny but has most of the mass
Some nitrogen atoms have seven neutrons and some have eight neutrons. These two forms of nitrogen are:
isotopes of each other.
The energy of a red photon is ____ the energy of a blue photon.
less than
Compared to their values on Earth, on another planet your
mass would be the same but your weight would be different.
In diagrams of the type shown, the electron that loses the most energy is the one that __________.
moves the greatest distance between the energy levels (blue circles) in its downward transition
If a hot gas cloud is moving across the sky (neither towards us or away from us), the emission lines would be
neither blue shifted nor red shifted
The neon "OPEN" sign appears reddish-orange because __________.
neon atoms emit many more yellow and red photons than blue and violet photons
The interior of the Sun effectively produces a continuous spectrum. These photons escape to space __________.
only after passing through a thin, cooler layer of gas atthe Sun's surface
A spectral line that appears at a wavelength of 321 nm in the laboratory appears at a wavelength of 328 nm in the spectrum of a distant object. We say that the object's spectrum is:
redshifted
Which of the following forms of light can be observed with telescopes at sea level?
visible light and radio waves
if the angular separation of two stars is larger than the angular resolution of your eyes:
you will be able to see both stars