Quiz CH 5

Currently, the largest optical telescope mirrors have a diameter of

10 m

An atom of the element iron has an atomic number of 26 and an atomic mass number of 56. If it is neutral, how many protons, neutrons, and electrons does it have?

26 protons, 30 neutrons, 26 electrons

Which of the following is least reasonable regarding our perception of color?

A banana which appears yellow in white light would appear blue when illuminated by blue light.

Which of the following statements about thermal radiation is always true?

A hot object emits more radiation per unit surface area than a cool object.

Which of the following statements about thermal radiation is always true?

A hot object emits photons with a higher average energy than a cool object.

Which of the following statements about electrical charge is true?

A positive charge and a negative charge will attract each other.

We refer to the ranges of wavelengths in the spectrum that can pass through the atmosphere as "windows." Which of the following is least reasonable regarding atmospheric windows?

Astronomers can only study radio waves and visible light using detectors mounted on weather balloons, in rockets, or in Earth-orbiting satellites.

Each of the following describes an "Atom 1" and an "Atom 2." In which case are the two atoms different isotopes of the same element?

Atom 1: nucleus with 7 protons and 8 neutrons, surrounded by 7 electrons.Atom 2: nucleus with 7 protons and 7 neutrons, surrounded by 7 electrons.

Which of the following is least reasonable regarding cosmic background radiation (CBR)?

CBR correponds to a solar temperature of about 6,000 degrees and implies that the Universe was about 3K right after the Big Bang.

The largest effective telescope, created by radio interferometry, is the size of

Earth

Which of the following statements about electrons is not true?

Electrons orbit the nucleus rather like planets orbiting the Sun.

Which of the following statements is true of green grass?

It absorbs red light and reflects green light.

What is the purpose of interferometry?

It allows two or more small telescopes to achieve the angular resolution of a much larger telescope.

Which of the following is not an advantage of the Hubble Space Telescope over ground-based telescopes?

It is closer to the stars.

What is the purpose of adaptive optics?

It reduces blurring caused by atmospheric turbulence for telescopes on the ground.

How can an electron in an atom lose energy to go from a higher energy level to a lower energy level?

It releases a photon equal in energy to its own energy drop.

Betelgeuse is the bright red star representing the left shoulder of the constellation Orion. All the following statements about Betelgeuse are true. Which one can you infer from its red color?

Its surface is cooler than the surface of the Sun.

What do astronomers mean by light pollution?

Light pollution refers to lights from human sources that make it difficult to see the stars at night.

How are wavelength, frequency, and energy related for photons of light?

Longer wavelength means lower frequency and lower energy.

Which of the following statements about X rays and radio waves is not true?

Neither X rays nor radio waves can penetrate Earth's atmosphere.

Why do astronomers need different telescope designs to observe across the electromagnetic spectrum?

Photons of different energy behave differently and require different collection strategies.

Suppose that the angular separation of two stars is 0.1 arcsecond, and you photograph them with a telescope that has an angular resolution of 1 arcsecond. How will the stars appear in the photograph?

Since their angular separation is smaller than the telescope's angular resolution, your photograph will seem to show only one star rather than two.

Suppose that Star X and Star Y both have redshifts, but Star X has a larger redshift than Star Y. What can you conclude?

Star X is moving away from us faster than Star Y.

Which of the following statements best describes the two principle advantages of telescopes over eyes?

Telescopes can collect far more light with far better angular resolution.

How does the light-collecting area of an 8-meter telescope compare to that of a 2-meter telescope?

The 8-meter telescope has 16 times the light-collecting area of the 2-meter telescope.

Consider an atom of gold in which the nucleus contains 79 protons and 118 neutrons. What is its atomic number and atomic mass number?

The atomic number is 79, and the atomic mass number is 197.

Suppose you see two stars: a blue star and a red star. Which of the following can you conclude about the two stars? Assume that no Doppler shifts are involved. (Hint: Think about the laws of thermal radiation.)

The blue star has a hotter surface temperature than the red star.

Which of the following conditions lead you to see an absorption line spectrum from a cloud of gas in interstellar space?

The cloud is cool and lies between you and a hot star.

If an electron at level 1 in a hydrogen atom absorbs 10.2 eV of energy, it moves to level 2. What typically happens next?

The electron returns to level 1 by emitting an ultraviolet photon with 10.2 eV of energy.

Which of the following best describes why we say that light is an electromagnetic wave?

The passage of a light wave can cause electrically charged particles to move up and down.

If we observe one edge of a planet to be redshifted and the opposite edge to be blueshifted, what can we conclude about the planet?

The planet is rotating.

From laboratory measurements, we know that a particular spectral line formed by hydrogen appears at a wavelength of 121.6 nanometers (nm). The spectrum of a particular star shows the same hydrogen line appearing at a wavelength of 121.8 nm. What can we conclude?

The star is moving away from us.

From laboratory measurements, we know that a particular spectral line formed by hydrogen appears at a wavelength of 486.1 nanometers (nm). The spectrum of a particular star shows the same hydrogen line appearing at a wavelength of 486.0 nm. What can we conclude?

The star is moving toward us.

Studying a spectrum from a star can tell us a lot. All of the following statements are true except one. Which one?

The total amount of light in the spectrum tells us the star's radius.

Which of the following is always true about images captured with X-ray telescopes?

They are always shown with colors that are not the true colors of the objects that were photographed.

Which of the following objects is not a close approximation of a thermal emitter?

Which of the following objects is not a close approximation of a thermal emitter?

The Chandra X-ray Observatory must operate in space because

X rays do not penetrate Earth's atmosphere

Which of the following statements about X rays and radio waves is not true?

X rays travel through space faster than radio waves.

Typical stellar spectra appear as:

a rainbow, but with some dark lines mixed in.

What is the angular resolution of the human eye?

about 1 arcminute, or 1/60 of a degree

An electron-volt is

an amount of energy much smaller than a joule.

What is spectroscopy?

an analysis of the way in which atoms absorb and emit light

If you heat a gas so that collisions are continually bumping electrons to higher energy levels, when the electrons fall back to lower energy levels the gas produces

an emission line spectrum.

Which of these produces the classic continuous spectrum?

an incandescent light bulb

According to Wien's Law, if the surface temperature is increased by a factor of 2, its peak wavelength will

decrease by a factor of 2.

When an electron in an atom goes from a higher energy state to a lower energy state, the atom

emits a photon of a specific frequency.

Spectra from neutral atoms compared with spectra from ionized atoms of the same element

have different sets of spectral lines.

When an atom loses an electron, it becomes

ionized

How many atoms fit across the period at the end of this sentence?

millions

A gas heated to millions of degrees would emit

mostly X rays.

Compared to the size of its nucleus, the size of an atom is typically about

one hundred thousand times greater.

In what part of the electromagnetic spectrum do the biggest telescopes on Earth operate?

radio

In what wavelength range was interferometry first routinely used?

radio

From lowest energy to highest energy, which of the following correctly orders the different categories of electromagnetic radiation?

radio, infrared, visible light, ultraviolet, X rays, gamma rays

We can see each other in the classroom right now because we

reflect visible light.

Without telescopes or other aid, we can look up and see the Moon in the night sky because it

reflects visible light.

Suppose you built a scale-model atom in which the nucleus is the size of a tennis ball. About how far would the cloud of electrons extend?

several kilometers

The wavelength of a wave is

the distance between two adjacent peaks of the wave.

Everything looks red through a red filter because

the filter transmits red light and absorbs other colors.

The frequency of a wave is

the number of peaks passing by any point each second; measured in cycles per second; measured in hertz (Hz); equal to the speed of the wave divided by the wavelength of the wave.

Which of the following is not a good reason to place observatories on remote mountain tops?

to be able to observe at radio wavelengths

The following diagram represents energy levels in a hydrogen atom. The labeled transitions (A through E) represent an electron moving between energy levels. Which labeled transition represents an electron in the ground state (lowest energy level) that absorbs a photon with 10.2 eV of energy and how much more energy would this electron need to absorb to become completely dislodged from the atom (ionization)?

transition C, 3.4 eV more

If a material is transparent, then it

transmits light well.

The stars in our sky twinkle in brightness and color because of

turbulence in Earth's atmosphere.