Question 1

Why is the sky blue?

Accepted Answer

A)  The air molecules absorb red light more effectively than blue light, allowing more blue light to reach observers on Earth's surface. 
B)  The air molecules scatter blue light more effectively than red light, so more blue light reaches observers on Earth's surface indirectly (from directions other than the direct beam of sunlight). 
C)  The air molecules scatter red light more effectively than blue light, so less red light reaches observers on Earth's surface indirectly (from directions other than the direct beam of sunlight). 
D)  The air molecules absorb blue light more effectively than red light, making the sky appear bluer. 
A)  The air molecules absorb red light more effectively than blue light, allowing more blue light to reach observers on Earth's surface. 
B)  The air molecules scatter blue light more effectively than red light, so more blue light reaches observers on Earth's surface indirectly (from directions other than the direct beam of sunlight). 
C)  The air molecules scatter red light more effectively than blue light, so less red light reaches observers on Earth's surface indirectly (from directions other than the direct beam of sunlight). 
D)  The air molecules absorb blue light more effectively than red light, making the sky appear bluer.

Question 2

An atom in which one or more electrons has been removed is known as a(n)

Accepted Answer

A)  molecule. 
B)  excited atom. 
C)  isotope. 
D)  ion. 
A)  molecule. 
B)  excited atom. 
C)  isotope. 
D)  ion.

Question 3

Why does the Sun look red when it is setting?

Accepted Answer

A)  Red is the Sun's natural color as determined by Wien's law, but it is only when the Sun is close to the horizon that sunlight can pass through the atmosphere unfiltered. 
B)  When the Sun is close to the horizon, it is traveling away from the observer at great speed, and the Doppler shift makes it look red. 
C)  Earth's atmosphere scatters longer wavelength light more easily than shorter, so more red light is scattered out of the sunlight and into observers' eyes. 
D)  Earth's atmosphere scatters shorter wavelength light more easily than longer, so more red light is left to reach observers' eyes. 
A)  Red is the Sun's natural color as determined by Wien's law, but it is only when the Sun is close to the horizon that sunlight can pass through the atmosphere unfiltered. 
B)  When the Sun is close to the horizon, it is traveling away from the observer at great speed, and the Doppler shift makes it look red. 
C)  Earth's atmosphere scatters longer wavelength light more easily than shorter, so more red light is scattered out of the sunlight and into observers' eyes. 
D)  Earth's atmosphere scatters shorter wavelength light more easily than longer, so more red light is left to reach observers' eyes.

Question 4

The strong red spectral line emitted by hot hydrogen gas is known as the _____ line.

Accepted Answer

A)  21-cm 
B)  Balmer $\alpha$ 
C)  Lyman $\alpha$ 
D)  Paschen $\alpha$ 
A)  21-cm 
B)  Balmer $\alpha$ 
C)  Lyman $\alpha$ 
D)  Paschen $\alpha$

Question 5

One nucleus that will prove to be important in the study of the evolving universe is 56Fe. This isotope of iron has 26 electrons as a neutral atom. The nuclear isotope has

Accepted Answer

A)  26 protons and 56 neutrons. 
B)  26 protons and 30 neutrons. 
C)  56 protons and 26 neutrons. 
D)  56 protons and 30 neutrons. 
A)  26 protons and 56 neutrons. 
B)  26 protons and 30 neutrons. 
C)  56 protons and 26 neutrons. 
D)  56 protons and 30 neutrons.

Question 6

The total radiant energy emitted per unit area from a blackbody's surface is proportional to what power of the blackbody's Kelvin temperature?

Accepted Answer

A)  T 
B)  1/T 
C)  T2 
D)  T4 
A)  T 
B)  1/T 
C)  T2 
D)  T4

Question 7

In the hydrogen atom, light is emitted whenever an electron

Accepted Answer

A)  jumps from a lower to an upper energy level or orbit. 
B)  reverses its direction of motion in its orbit. 
C)  jumps from an upper to a lower energy level or orbit. 
D)  spirals into the nucleus. 
A)  jumps from a lower to an upper energy level or orbit. 
B)  reverses its direction of motion in its orbit. 
C)  jumps from an upper to a lower energy level or orbit. 
D)  spirals into the nucleus.

Question 8

A clear majority of the information astronomers obtain about distant astronomical objects comes from an analysis of

Accepted Answer

A)  cosmic rays. 
B)  meteorite fragments. 
C)  electromagnetic radiation. 
D)  radioactive decay products. 
A)  cosmic rays. 
B)  meteorite fragments. 
C)  electromagnetic radiation. 
D)  radioactive decay products.

Question 9

The element helium was first discovered and identified as a separate element

Accepted Answer

A)  in natural gas originating underground, from the spectrum emitted from a flame of burning natural gas. 
B)  in rocks containing radioactively decaying elements such as uranium. 
C)  on the Sun, from the emitted spectrum from its upper atmosphere. 
D)  inside meteorites that had come from outer space. 
A)  in natural gas originating underground, from the spectrum emitted from a flame of burning natural gas. 
B)  in rocks containing radioactively decaying elements such as uranium. 
C)  on the Sun, from the emitted spectrum from its upper atmosphere. 
D)  inside meteorites that had come from outer space.

Question 10

The wavelength $\lambda$0 of light emitted by a moving object is detected as a different wavelength $\lambda$ by a stationary observer. If v is the velocity of the object and c is the velocity of light, this Doppler shift can be described by the equation

Accepted Answer

A)  ($\lambda$ - $\lambda$0 = v - c.) 
B)  ($\lambda$/$\lambda$0 = v/c.) 
C)  ($\lambda$$\lambda$0 = vc.) 
D)  ($\lambda$ - $\lambda$0)/$\lambda$0 = v/c.) 
A)  ($\lambda$ - $\lambda$0 = v - c.) 
B)  ($\lambda$/$\lambda$0 = v/c.) 
C)  ($\lambda$$\lambda$0 = vc.) 
D)  ($\lambda$ - $\lambda$0)/$\lambda$0 = v/c.)

Question 11

What is a diffraction grating?

Accepted Answer

A)  flat, rectangular array of closely spaced photosensitive cells 
B)  piece of glass with thousands of closely spaced, parallel grooves 
C)  array of many radio telescopes used to observe a single source simultaneously 
D)  triangular prism of solid glass used to disperse light into its colors 
A)  flat, rectangular array of closely spaced photosensitive cells 
B)  piece of glass with thousands of closely spaced, parallel grooves 
C)  array of many radio telescopes used to observe a single source simultaneously 
D)  triangular prism of solid glass used to disperse light into its colors

Question 12

To use Wien's law to find the temperature of an object, one needs to know

Accepted Answer

A)  the object's distance. 
B)  the object's mass. 
C)  the wavelength in the spectrum of the object at which the intensity is greatest. 
D)  the frequency of the most energetic photons emitted from the object. 
A)  the object's distance. 
B)  the object's mass. 
C)  the wavelength in the spectrum of the object at which the intensity is greatest. 
D)  the frequency of the most energetic photons emitted from the object.

Question 13

The mass of the proton, the nucleus of the hydrogen atom, exceeds the mass of the electron by approximately what factor?

Accepted Answer

A)  2000 times 
B)  10,000 times 
C)  100 times 
D)  2 times 
A)  2000 times 
B)  10,000 times 
C)  100 times 
D)  2 times

Question 14

A perfect blackbody is so named because it

Accepted Answer

A)  reflects all radiation falling upon it but emits none of its own. 
B)  absorbs all radiation falling upon it and reflects none. 
C)  never emits radiation. 
D)  always emits the same amount and color of radiation regardless of its temperature. 
A)  reflects all radiation falling upon it but emits none of its own. 
B)  absorbs all radiation falling upon it and reflects none. 
C)  never emits radiation. 
D)  always emits the same amount and color of radiation regardless of its temperature.

Question 15

Which one of these temperatures is hottest?

Accepted Answer

A)  100 K 
B)  100°C 
C)  100°F 
D)  They are all the same. 
A)  100 K 
B)  100°C 
C)  100°F 
D)  They are all the same.

Question 16

A physicist is asked to design an infrared system to detect human beings (at a normal temperature of 310 K) in darkness. What would the wavelength of peak sensitivity of the equipment need to be?

Accepted Answer

A)  9.35 $\mu$m 
B)  0.935 $\mu$m 
C)  0.00094 $\mu$m 
D)  90 $\mu$m 
A)  9.35 $\mu$m 
B)  0.935 $\mu$m 
C)  0.00094 $\mu$m 
D)  90 $\mu$m

Question 17

Stars A and B have the same radius, but the spectrum of star A peaks at a wavelength of 500 nm, whereas star B's spectrum peaks at 1000 nm. What is the ratio of the energy flux leaving the surface of star A to the energy flux leaving the surface of star B?

Accepted Answer

A)  1/16 
B)  1/4 
C)  4 
D)  16 
A)  1/16 
B)  1/4 
C)  4 
D)  16

Question 18

When light passes through a prism of glass, the

Accepted Answer

A)  different colors or wavelengths of light are separated in angle by the prism. 
B)  different colors are caused by multiple reflections in the prism and interference between the resulting beams. 
C)  prism absorbs colors from different parts of the broad beam coming out of the prism, leaving the complementary colors observed. 
D)  prism adds colors to different parts of the broadly scattered beam coming out of it. 
A)  different colors or wavelengths of light are separated in angle by the prism. 
B)  different colors are caused by multiple reflections in the prism and interference between the resulting beams. 
C)  prism absorbs colors from different parts of the broad beam coming out of the prism, leaving the complementary colors observed. 
D)  prism adds colors to different parts of the broadly scattered beam coming out of it.

Question 19

When a rod of metal is heated intensely, its predominant color will

Accepted Answer

A)  remain red as the intensity of light increases. 
B)  change from red through orange to white and then to blue. 
C)  change from blue through white, then orange, and finally red, when it becomes red-hot at its hottest. 
D)  be white, all colors mixed together, as the intensity of light increases. 
A)  remain red as the intensity of light increases. 
B)  change from red through orange to white and then to blue. 
C)  change from blue through white, then orange, and finally red, when it becomes red-hot at its hottest. 
D)  be white, all colors mixed together, as the intensity of light increases.

Question 20

How do the nuclei of the isotopes 14C of carbon and 14N of nitrogen differ from each other?

Accepted Answer

A)  The nuclei have the same number of protons but a different number of neutrons. 
B)  The nuclei are identical; the isotopes differ only in the number of electrons. 
C)  The nuclei have different numbers of both protons and neutrons. 
D)  The nuclei have the same number of neutrons but a different number of protons. 
A)  The nuclei have the same number of protons but a different number of neutrons. 
B)  The nuclei are identical; the isotopes differ only in the number of electrons. 
C)  The nuclei have different numbers of both protons and neutrons. 
D)  The nuclei have the same number of neutrons but a different number of protons.

Why is the sky blue?

An atom in which one or more electrons has been removed is known as a(n)

Why does the Sun look red when it is setting?

The strong red spectral line emitted by hot hydrogen gas is known as the _____ line.

One nucleus that will prove to be important in the study of the evolving universe is ⁵⁶Fe. This isotope of iron has 26 electrons as a neutral atom. The nuclear isotope has

The total radiant energy emitted per unit area from a blackbody's surface is proportional to what power of the blackbody's Kelvin temperature?

In the hydrogen atom, light is emitted whenever an electron

A clear majority of the information astronomers obtain about distant astronomical objects comes from an analysis of

The element helium was first discovered and identified as a separate element

The wavelength $\lambda$ ₀ of light emitted by a moving object is detected as a different wavelength $\lambda$ by a stationary observer. If v is the velocity of the object and c is the velocity of light, this Doppler shift can be described by the equation

What is a diffraction grating?

To use Wien's law to find the temperature of an object, one needs to know

The mass of the proton, the nucleus of the hydrogen atom, exceeds the mass of the electron by approximately what factor?

A perfect blackbody is so named because it

Which one of these temperatures is hottest?

A physicist is asked to design an infrared system to detect human beings (at a normal temperature of 310 K) in darkness. What would the wavelength of peak sensitivity of the equipment need to be?

Stars A and B have the same radius, but the spectrum of star A peaks at a wavelength of 500 nm, whereas star B's spectrum peaks at 1000 nm. What is the ratio of the energy flux leaving the surface of star A to the energy flux leaving the surface of star B?

When light passes through a prism of glass, the

When a rod of metal is heated intensely, its predominant color will

How do the nuclei of the isotopes ¹⁴C of carbon and ¹⁴N of nitrogen differ from each other?

Discovering the Night Sky

Gravitation and the Motion of the Planets

Light and Telescopes

Exoplanets and the Formation of Planetary Systems

Formation of the Solar System

Earth and the Moon

The Other Terrestrial Planets

The Outer Planets

Vagabonds of the Solar System

The Sun: Our Extraordinary Star

Characterizing Stars

The Lives of Stars From Birth Through Middle Age

The Death of Stars

Black Holes: Matters of Gravity

The Milky Way Galaxy

Galaxies

Quasars and Other Active Galaxies

Cosmology

Astrobiology

Filters

Exam 4: Atomic Physics and Spectra

Why is the sky blue?

An atom in which one or more electrons has been removed is known as a(n)

Why does the Sun look red when it is setting?

The strong red spectral line emitted by hot hydrogen gas is known as the _____ line.

One nucleus that will prove to be important in the study of the evolving universe is 56Fe. This isotope of iron has 26 electrons as a neutral atom. The nuclear isotope has

The total radiant energy emitted per unit area from a blackbody's surface is proportional to what power of the blackbody's Kelvin temperature?

In the hydrogen atom, light is emitted whenever an electron

A clear majority of the information astronomers obtain about distant astronomical objects comes from an analysis of

The element helium was first discovered and identified as a separate element

The wavelength λ\lambdaλ 0 of light emitted by a moving object is detected as a different wavelength λ\lambdaλ by a stationary observer. If v is the velocity of the object and c is the velocity of light, this Doppler shift can be described by the equation

What is a diffraction grating?

To use Wien's law to find the temperature of an object, one needs to know

The mass of the proton, the nucleus of the hydrogen atom, exceeds the mass of the electron by approximately what factor?

A perfect blackbody is so named because it

Which one of these temperatures is hottest?

A physicist is asked to design an infrared system to detect human beings (at a normal temperature of 310 K) in darkness. What would the wavelength of peak sensitivity of the equipment need to be?

Stars A and B have the same radius, but the spectrum of star A peaks at a wavelength of 500 nm, whereas star B's spectrum peaks at 1000 nm. What is the ratio of the energy flux leaving the surface of star A to the energy flux leaving the surface of star B?

When light passes through a prism of glass, the

When a rod of metal is heated intensely, its predominant color will

How do the nuclei of the isotopes 14C of carbon and 14N of nitrogen differ from each other?

Discovering the Night Sky

Gravitation and the Motion of the Planets

Light and Telescopes

Exoplanets and the Formation of Planetary Systems

Formation of the Solar System

Earth and the Moon

The Other Terrestrial Planets

The Outer Planets

Vagabonds of the Solar System

The Sun: Our Extraordinary Star

Characterizing Stars

The Lives of Stars From Birth Through Middle Age

The Death of Stars

Black Holes: Matters of Gravity

The Milky Way Galaxy

Galaxies

Quasars and Other Active Galaxies

Cosmology

Astrobiology

Filters

One nucleus that will prove to be important in the study of the evolving universe is ⁵⁶Fe. This isotope of iron has 26 electrons as a neutral atom. The nuclear isotope has

The wavelength $\lambda$ ₀ of light emitted by a moving object is detected as a different wavelength $\lambda$ by a stationary observer. If v is the velocity of the object and c is the velocity of light, this Doppler shift can be described by the equation

How do the nuclei of the isotopes ¹⁴C of carbon and ¹⁴N of nitrogen differ from each other?