Deck 4: A Universe of Universal Laws

Question 1

What property of a star allows you to measure its composition?

A) the brightest color in its spectrum
B) the wavelengths of its absorption lines
C) its luminosity
D) its mass

Answer 1

the wavelengths of its absorption lines

Question 2

Place the following varieties of light in order,from lowest to highest frequency: infrared,ultraviolet,microwave,visible,gamma rays.

A) infrared, gamma ray, ultraviolet, visible, microwave
B) microwave, infrared, visible, ultraviolet, gamma ray
C) gamma ray, ultraviolet, infrared, visible, microwave
D) infrared, visible, microwave, ultraviolet, gamma ray

Answer 2

microwave, infrared, visible, ultraviolet, gamma ray

Question 3

An opaque cloud of dust at 10 K will emit:

A) a continuous spectrum.
B) an emission line spectrum.
C) an absorption line spectrum.
D) no light.

Answer 3

a continuous spectrum.

Question 4

Which of the following causes blackbody radiation?

A) gravitational potential energy
B) thermal energy
C) latent heat
D) free energy

Question 5

A low-density tube of neon gas at room temperature is placed in front of a hot metal rod.An observer will find:

A) a continuous spectrum.
B) an emission line spectrum.
C) an absorption line spectrum.
D) no light.

Question 6

What is the wavelength of the wave shown in the figure below?

A) 8 m
B) 4 m
C) 2 m
D) 1 m

Question 7

An astronomer measures the spectra of two stars,A and B.She finds that star A is nine times more luminous than star B and is three times as hot.How are their surface areas related?

A) Star A's area is three times larger than star B's.
B) Star A's area is two times larger than star B's.
C) Star A's area is the same size as star B's.
D) Star A's area is three times smaller than star B's.

Question 8

Which of the following varieties of light has the LOWEST frequency?

A) green
B) yellow
C) blue
D) red

Question 9

A wave in the electromagnetic field is:

A) light.
B) an electron.
C) radioactivity.
D) an ion.

Question 10

The radiation spectrum produced by a blackbody depends on its:

A) temperature.
B) composition.
C) mass.
D) thickness.

Question 11

Two light waves have wavelengths of 200 nm and 400 nm,respectively.How are their frequencies related?

A) The wave with a 200 nm wavelength has one-quarter the frequency of the 400 nm wave.
B) The wave with a 200 nm wavelength has one-half the frequency of the 400 nm wave.
C) The wave with a 200 nm wavelength has the same frequency of the 400 nm wave.
D) The wave with a 200 nm wavelength has twice the frequency of the 400 nm wave.

Question 12

A spectrograph measures the:

A) speed of a light beam.
B) energy carried by each component wavelength of a light beam.
C) polarization of a light beam.
D) atmospheric distortion experienced by a light beam.

Question 13

The speed of a light wave:

A) increases with its frequency.
B) increases with its wavelength.
C) decreases with its amplitude.
D) is independent of its other properties.

Question 14

An iron rod heated to 3,000 K will emit a(n)________ spectrum.

A) continuous
B) emission line
C) absorption line
D) band

Question 15

A spectrum of an unknown material reveals discrete bright lines with long,dark gaps between them.Which of the following could describe the unknown material?

A) a hot cooking pot
B) cool chicken noodle soup
C) steam
D) ice made opaque by high pressures

Question 16

Which of the following varieties of light has the SHORTEST wavelength?

A) ultraviolet
B) infrared
C) microwave
D) visible

Question 17

An astronomer measures the spectrum of a star and finds that it emits the most intense light at 0.5 mm.What is its temperature?

A) 1,000 K
B) 3,000 K
C) 6,000 K
D) 9,000 K

Question 18

An astronomer obtains two samples of rarefied gas.She heats the first gas and finds that it produces a spectra with a series of bright lines.She places the other gas in front of a hot blackbody and finds a continuous spectrum with a series of dark lines.If the wavelengths of the dark lines are the same as those of the bright lines,she infers that the samples have identical:

A) reflectivity.
B) opacity.
C) compositions.
D) temperatures.

Question 19

If the wave shown in the figure below travels to the left with a speed of 8 m/s,what is its frequency?

A) 8 Hz
B) 4 Hz
C) 2 Hz
D) 1 Hz

Question 20

An astronomer measures the luminosities of two stars with identical sizes,finding that star A is 256 times as luminous as star B.How are their temperatures related to each other?

A) Star A is twice as hot as star B.
B) Star A is 4 times hotter than star B.
C) Star A is 16 times hotter than star B.
D) Star A is 64 times hotter than star B.

Question 21

Among the following,which is the most important reason to make telescopes large?

A) atmospheric seeing
B) chromatic aberration
C) magnification
D) light-collecting power

Question 22

Which of the following objects would emit the most radiation?

A) A 1 m2 block of molten iron at 6,000 K.
B) A 0.5 m2 block of molten nickel at 6,000 K.
C) A 2 m2 block of molten iron at 1,500 K.
D) A 6 m2 block of molten nickel at 3,000 K.

Question 23

The H alpha line of hydrogen produces photons in what part of the electromagnetic spectrum?

A) ultraviolet
B) blue
C) red
D) infrared

Question 24

Which of the following is NOT true of the Bohr model of the atom?

A) Electrons can orbit the nucleus at any radius, as in the solar system.
B) Atomic nuclei consist of protons and neutrons.
C) Electrons can move their orbits by absorbing or emitting light.
D) Electrons travel on circular orbits.

Question 25

The Lyman series refers to:

A) the photons produced as an electron makes a series of jumps from a high excited state to the ground state of hydrogen.
B) the discrete orbits in the hydrogen atom.
C) electronic transitions between the ground state and excited states of hydrogen.
D) electronic transitions in the hydrogen atom that produce light in the visible part of the spectrum.

Question 26

Stars A and B have identical luminosities,but star A is twice as far away as star B.How does the brightness of these two stars compare?

A) Star A is two times brighter than star B.
B) Star A is four times brighter than star B.
C) Star A is two times fainter than star B.
D) Star A is four times fainter than star B.

Question 27

The figure below shows a model of an atom.Which of the following electron transitions would release a photon with the most energy?

A) 2 to 1
B) 4 to 1
C) 1 to 2
D) 1 to 4

Question 28

Among the following,the best angular resolution will be achieved with a ________ diameter telescope observing in ________ light.

A) 10-m; blue
B) 10-m; red
C) 1-m; blue
D) 1-m; red

Question 29

Which of the following is NOT an advantage of a reflecting telescope over a refracting telescope?

A) Mirrors suffer less chromatic aberration than lenses.
B) Reflecting telescopes can be made shorter than refracting telescopes.
C) Mirrors provide stronger magnification than lenses.
D) Reflecting telescopes can support larger mirrors.

Question 30

An astronomer takes a spectrum of a nearby star.She finds that its absorption lines all appear at shorter wavelengths than expected from laboratory measurements.She should conclude that the star is:

A) moving toward her.
B) composed of elements not seen on Earth.
C) hotter than her laboratory analogs.
D) obscured by dust.

Question 31

Light is:

A) a wave in the electromagnetic field.
B) a particle.
C) both a particle and a wave.
D) neither particle nor wave.

Question 32

Stars A is four times more luminous than star B,and it is also four times farther away than star B.How does the brightness of these two stars compare?

A) Star A is 4 times fainter than star B.
B) Star A is 16 times fainter than star B.
C) Star A is 4 times brighter than star B.
D) Star A is 16 times brighter than star B.

Question 33

Which of the following properties of an astronomical image will improve if the image is made in blue light instead of red light,if all other factors are held constant?

A) magnification
B) angular resolution
C) light-collecting power
D) polarization

Question 34

Stars A and B have identical luminosities,but star A is nine times brighter than star B.If star A is 9 parsecs from Earth,how far away is star B?

A) 1 parsec
B) 3 parsecs
C) 27 parsecs
D) 81 parsecs

Question 35

The figure below shows a model of an atom.If an electron begins in orbit #1,moves to orbit #4,then moves to orbit #3,and then to orbit #1,how has it interacted with light?

A) It has emitted a high energy photon and absorbed two low energy photons.
B) It has absorbed a high energy photon and emitted two low energy photons.
C) It has absorbed a photon and emitted two photons, all with identical energies.
D) It has emitted a photon and absorbed two photons, all with identical energies.

Question 36

If your pupil is 1 cm across,how large does a telescope aperture have to be to collect one million times more light than your eye?

A) 10 cm
B) 1 m
C) 10 m
D) 100 m

Question 37

What kind of telescope is shown in the figure below? Here the arrows show the path of light rays through the telescope and "F" labels the focus point.

A) refracting
B) reflecting
C) Newtonian
D) chromatic

Question 38

A standard candle allows astronomers to measure:

A) brightness.
B) temperature.
C) distance.
D) age.

Question 39

An atom will emit a photon when an electron:

A) completes an orbit.
B) shifts from the ground state to an excited state.
C) falls into the nucleus.
D) moves from an outer orbit to an inner orbit.

Question 40

A gas cloud has an emission spectrum.If all of its lines appear at higher photon energies than expected from a comparison to laboratory measurements,the cloud is:

A) cooler than the laboratory gas.
B) hotter than the laboratory gas.
C) moving away from the observer.
D) moving toward the observer.

Question 41

A telescope with a diameter of 2 m is just barely able to resolve features on a gas cloud when observing it at 500 nm wavelength.Which of the following observations would also just barely be able to resolve these features?

A) a 1-m diameter telescope observing at 1,000 nm
B) a 4-m diameter telescope observing at 125 nm
C) a 4-m diameter telescope observing at 250 nm
D) a 1-m diameter telescope observing at 250 nm

Question 42

A rubber ball falls from a height of 1,000 m,accelerates,and then impacts Earth.During the impact,it heats up so much that it melts.The melted rubber glows and eventually cools off.How would you describe the flow of energy in this scenario?

Question 43

A reading light contains a dimmer switch that can vary its luminosity from 10 W to 100 W.If the device produces just the right amount of light when set to 10 W and held at a distance of 10 centimeters,to what value should you set the wattage if you hold it 20 centimeters away?

Question 44

Modern astronomical observatories sometimes shine lasers into the sky because they:

A) help guide the pointing of the telescope.
B) allow corrections of atmospheric turbulence.
C) decrease the atmospheric opacity.
D) calibrate spectroscopes.

Question 45

What does thermal energy represent?

Question 46

An astronomer takes spectra of two stars,A and B.Star A's spectrum peaks at 200 nm,while star B's spectrum peaks at 800 nm.If the stars have identical sizes,how do their luminosities compare?

Question 47

An astronomer takes spectra of two stars,A and B.She discovers that the continuous part of star A's spectrum peaks at 200 nm,while the continuous part of star B's spectrum peaks at 800 nm.Both stars have dark bands superposed on this continuous spectrum,and the locations of these dark bands are the same in both stars.What do you know about the composition of the stars? Why?

Question 48

Which of the following portions of the electromagnetic spectrum must be observed from space?

A) ultraviolet
B) radio
C) near infrared
D) visible

Question 49

How would you use a star's spectrum to measure its temperature?

Question 50

A pair of radio dishes,each with collecting area 100 m²,lie a distance of 10 km from each other.With them,astronomers can make a measurement with an effective collecting area of ________ and an effective angular resolution of a telescope with a ________ diameter.

A) 10⁸ m²; 200 m
B) 10⁸ m²; 200 m.
C) 200 m²; 10 km
D) 200 m²; 10 km.

Question 51

The Chandra X-Ray Observatory achieves high angular resolution with:

A) interferometry.
B) a large diameter aperture.
C) grazing incidence mirrors.
D) lead plates that block unwanted X-rays.

Question 52

Consider the experiment shown in the figure below.Describe the spectra observed by Spectrographs A,B,and C.

Question 53

Which of the following sites would make the best location for an infrared telescope?

A) the South Pole
B) a deep valley
C) an arctic mountain
D) a high-altitude desert

Question 54

Type I supernovae all have (nearly)identical luminosities.Explain how this fact allows us to measure their distances.

Question 55

The practice of combining signals from two or more reflectors to achieve better angular resolution is:

A) adaptive optics.
B) interferometry.
C) refraction.
D) signal processing.

Question 56

Which of the following types of light has the highest atmospheric transmission?

A) radio
B) infrared
C) ultraviolet light
D) gamma rays

Question 57

List the seven components of the electromagnetic spectrum from shortest to longest wavelength.

Question 58

A particular water wave has an amplitude of 2 m and a wavelength of 3 m.With this wave,the time between successive crests hit shore is 2 seconds.What is the speed of the wave?

Question 59

An astronomer using a refracting telescope sees an image of two gas clouds with identical shapes but displaced slightly from each other.One is composed of blue light and the other red light.The most likely explanation is:

A) the Doppler effect.
B) chromatic aberration.
C) dust absorption.
D) interstellar scattering.

Question 60

Stars twinkle because of:

A) interstellar dust.
B) surface variations on the stars.
C) atmospheric turbulence.
D) opacity variations.

Question 61

Describe the path of light in a reflecting telescope with a Newtonian focus.

Question 62

A star moves rightward with a velocity of 100 m/s,as shown in the figure below.Observers stand at positions A,B,and C.Compared to reference wavelengths measured in the laboratory,how would each of these observers see the star's absorption lines shift?

Question 63

A telescope with a Cassegrain focus reflects light through an opening in the primary mirror for measurement at a camera.The telescope's mirror therefore has a small hole in it where light cannot be collected.How much smaller is the light-collecting power of a telescope with a primary mirror of diameter 10 m and a circular hole with a diameter of 1 m than an identical telescope without such a hole?

Question 64

An astronomer observes two stars,A and B.Star A has a temperature of 3,000 K,a radius 10 times that of our Sun,and is 10 parsecs away.Star B has a temperature of 6,000 K,a radius equal to that of our Sun,and is 40 parsecs away.Which star is brighter,and by how much?

Question 65

Which portions of the electromagnetic spectrum must be observed from space?

Question 66

Two stars are situated a distance 1 parsec apart.Both are a distance of 100 parsecs from Earth,as shown in the figure below.An astronomer would like to observe these stars individually with a radio telescope.Find the minimum diameter of her telescope if she decides to observe the stars at a wavelength of 1 m.

Question 67

The next generation of large near-infrared telescopes will be built at high,dry sites.List two reasons why.

Question 68

What are the constituents of an atom,and how are they arranged according to the Bohr model?

Question 69

A telescope can barely detect a star situated at 1 kpc from Earth.If an identical star were placed 4 kpc from Earth,how much larger would the radius of the telescope have to be to observe it?

Question 70

Consider the experiment shown in the figure below.Identify the spectra observed at spectrographs A and B,and explain how the Bohr model accounts for the features in these spectra.