Astronomy Chapter 5 Multiple Choice

If you have a 100-watt light bulb, how much energy does it use each minute?

6,000 joules

If a material is highly opaque, then it

absorbs most light.

When light reflects off an object, what is the relation between the angle of incidence and the angle of reflection?

angle of incidence = angle of reflection

If a material is transparent, then it

transmits light well.

Grass (that is healthy) looks green because

it reflects green light and absorbs other colors.

Everything looks red through a red filter because

the filter transmits red light and absorbs other colors.

Which of the following cannot be described by a field?

radiation pressure

The frequency of a wave is

all of the above

The wavelength of a wave is

the distance between two adjacent peaks of the wave.

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

Longer wavelength means lower frequency and lower energy.

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

From shortest to longest wavelength, which of the following correctly orders the different categories of electromagnetic radiation?

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

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

X rays travel through space faster than radio waves.

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

Neither X rays nor radio waves can penetrate the earth’s atmosphere.

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.

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

millions

What is a compound?

a molecule containing two or more elements

Compared to the volume of its nucleus, the volume of an atom is about

a trillion times greater.

How much electrical charge does an atom with 6 protons, 6 neutrons, and 5 electrons have?

a positive charge of +1

Which of the following statements about electrical charge is true?

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

Which of the following statements about electrons is not true?

Electrons orbit the nucleus rather like planets orbiting the Sun.

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

several kilometers

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

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

Consider an atom of gold in which the nucleus contains 79 protons and 118 neutrons. If it is doubly ionized, what is the charge of the gold ion and how many electrons remain in the ion?

The gold ion has a charge of +2 and 77 electrons.

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

Atom 1: nucleus with 92 protons and 143 neutrons, surrounded by 92 electrons Atom 2: nucleus with 92 protons and 146 neutrons, surrounded by 92 electrons

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

26 protons, 30 neutrons, 26 electrons

Oxygen has atomic number 8. How many times must an oxygen atom be ionized to create an
O+5 ion, and how many electrons will the ion have?

It must be ionized five times; it now has three electrons.

At extremely high temperatures (e.g., millions of degrees), which of the following best describes the phase of matter?

a plasma consisting of positively charged ions and free electrons

Sublimation is the process in which

molecules go from the solid phase to the gas phase.

Dissociation is the process in which

the bonds between atoms in a molecule are broken.

When an atom loses an electron, it becomes

ionized.

An atom in an excited state contains more of what type of energy than the same atom in the ground state?

electric potential energy

When an atom absorbs a photon containing energy, any of the following can happen except which?

An electron moves from an upper energy level to a lower one.

The loss of an electron from a neutral helium atom results in

ionized helium.

An electron-volt is

an amount of energy much smaller than a joule.

The study of energy levels in atoms is called

quantum mechanics.

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.

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.

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.

When white light passes through a cool cloud of gas, we see

an absorption line spectrum.

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

have different sets of spectral lines.

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

hot, thin gas

Thermal radiation is defined as

radiation that depends only on the emitting object’s temperature.

A perfectly opaque object that absorbs all radiation and reemits the absorbed energy as thermal radiation is

a thermal emitter.

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

A hot object emits more total 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.

If two objects are the same size but one object is 3 times hotter than the other object, the hotter object emits

81 times more energy.

A gas heated to millions of degrees would emit

mostly X rays.

We can learn a lot about the properties of a star by studying its spectrum. 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.

The spectra of most galaxies show redshifts. This means that their spectral lines

have wavelengths that are longer than normal.

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 485.9 nm. What can we conclude?

The star is moving toward us.

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

How does the spectrum of a molecule differ from the spectrum of an atom?

A molecule has additional spectral lines due to changes in its rotational and vibrational energies.

You observe a distant galaxy. You find that a spectral line normally found in the visible part of the spectrum is shifted toward the infrared. What do you conclude?

The galaxy is moving away from you.

If one object has a large redshift and another object has a small redshift, what can we conclude about these two objects?

The one with the large redshift is moving away from us faster than the one with the small redshift.

f 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.

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.

You observe the same spectral line in two stars that are identical in every way except that one rotates faster than the other. How does the spectral line differ between the two?

The line in the faster rotating star is broader.