Astronomy Ch 4 - Light and Atoms

Which spectrum is from the object that would look the reddest?

C - (t may emit less red light than the blue spectrum object, but the red spectrum object gives off much more red light than it does blue. This makes it look red to the eye)

Select all that are properties of light.

Light is made up of electric and magnetic energy. Light can travel through a vacuum. The speed of light in empty space is constant.

Select all the conditions that are the same in the way a continuous and an absorption-line spectrum might be produced and observed

Light with a continuous spectrum is emitted Light passes through a prism Hot, dense material is present

Select all the particles that make up the nucleus.

Neutrons Protons

The speed of light in a material is ____ than the speed of light in a vacuum.

always less - (Sometimes the reduction in speed is not much [such as light traveling through air] but light always slows down when traveling through a material)

Energy levels are ____

another name for electron orbitals

Light is a mix of___energy and ___energy.

electric magnetic

Atoms are held together by the electrical attraction between ____

electrons and the nucleus

If you observe light from a very hot, tenuous gas cloud heated by stars close to it, then you will see a(n) ___ spectrum.

emission-line

If you observe light from a very hot, tenuous gas cloud heated by stars close to it, then you will see a(n)___spectrum

emission-line

Match the numerical values for absolute zero with their appropriate temperature scales.

0 - Kelvin scale -273 - Celsius scale -460 - Fahrenheit scale

Rank these temperatures in order from hottest (top) to coldest (bottom).

1. 0 Celsius 2. 0 Fahrenheit 3.0 Kelvin

Look at the electron orbital diagram. Rank the electronic transitions in order from the smallest (top) to the largest (bottom) amount of energy absorbed

1. 3-4 2. 2-3 3. 2-4 4. 1-4

Arrange the elements in order by how common they are in the Sun, with the most common on top and the least common on bottom.

1. Hydrogen 2. Helium 3. Oxygen 4. Carbon 5. Neon

Put the following chemical elements in order from lowest number of protons in the nucleus (top) to the highest number (bottom).

1. Hydrogen 2. Helium 3. Carbon 4. Oxygen 5. Iron

Rank the colors of light in order starting with longest wavelength and ending with the shortest.

1. Red 2. Yellow 3. Blue 4. Violet

If you see a planet with a wavelength of maximum emission of 2.9 x 104 nm, then its temperature will be ___ K. (Enter a whole number. Use the version of Wien's law from the book.)

100

You observe a blue star and measure its temperature to be 10,000 K. At what wavelength of light is it the brightest?

290 nanometers - (2,900,000 K nm /10,000 K = 290 nm)

One photon has a wavelength of 200 nanometers, and another has a wavelength of 800 nanometers. The first photon has ___ times as much energy as the second.

4

Which atom described below is electrically neutral?

6 protons, 5 neutrons, 6 electrons

Why does atomic hydrogen have a relatively simple emission spectrum, whereas hydrogen gas (H2) has a more complex spectrum?

A hydrogen molecule can emit photons based on electron energy level as well as lines associated with vibration and rotation.

Select all the instruments that can be used to spread light out into its component colors (a spectrum).

A prism A grating

Wavelengths in the microwave portion of the electromagnetic spectrum are comparable in size to which of the following objects?

A referee's whistle A soccer ball The width of a blade of grass

The picture shows what kind of spectrum?

Absorption-line - (absorption lines are the missing colors against the continuous background)

Match the terms with their definitions.

Atomic number - Number of protons in nucleus Electron - Small, negatively charged particle orbiting nucleus Proton - Positively charged particle in nucleus Ground state - Smallest possible orbit of an electron

Match each type of spectrum with its correct description

Continuous - All colors are present; formed by dense materials Emission-line - Only specific colors are present; formed by hot, thin gases Absorption-line - Almost all colors are present, but specific colors are dim or missing; formed by cooler gases

Match each type of spectrum with the kind of object that emits it.

Continuous - Filament of an incandescent lightbulb Emission-line - Hot, tenuous interstellar gas cloud Absorption-line - Cooler gas cloud in front of a much hotter object

Select all the objects below that are blackbodies or are nearly blackbodies.

Earth The Sun A piece of charcoal

The picture shows what kind of spectrum?

Emission-line

Why can astronomers use the spectrum of an object to identify what elements it contains?

Every element emits or absorbs a unique set of spectral line colors

True or false: Redder blackbodies are hotter than bluer ones.

False - (according to Wien's law, hotter objects will emit at shorter wavelengths, which are bluer colors)

Select all the types of astronomical objects from which astronomers have detected radio waves

Forming stars Supernovas (exploding stars) Interstellar gas clouds Active galaxies

Match each electromagnetic wave with its appropriate position on the spectrum.

Gamma ray - A X ray - B Ultraviolet - C Visible - D Infrared - E Radio - F

Match the units to the properties of light that they measure.

Joule (J) - Energy Hertz (Hz) - Frequency Nanometer (nm) - Wavelength Meters per second (m/sec) - Speed

Select all the circumstances under which spectral lines can form.

Molecules radiating light Solid objects reflecting light Molecules absorbing light Individual atoms radiating light Individual atoms absorbing light

Protons and neutrons are found in the ____ of an atom.

Nucleus

Select all the statements that correctly describe electron orbitals.

Orbitals describe the probability of finding the electron at different positions Electron orbitals are quantized Electron orbitals are very small

In order to calculate the energy of a photon, you need to know _____

Planck's constant, h it's wavelength, λ the speed of light, c

Select all of the following that correctly describe blackbodies.

They absorb all electromagnetic waves that fall on them. When warm, they emit all wavelengths of electromagnetic waves.

True or false: Astronomers can observe radio waves from interstellar gas clouds.

True

True or false: Light can travel through empty space.

True - (Light is radiant energy and can travel through space without a medium such as air or water)

True or false: Protons and electrons are attracted to one another.

True - (Protons are positively charged, electrons negatively charged; and opposite charges attract)

True or false: Short wavelength photons carry more energy than long wavelength ones.

True - (radio waves have much less energy than X rays or gamma rays)

Which types of telescopes must be placed above Earth's atmosphere? (Select all that apply.)

Ultraviolet Gamma ray X ray

Which of the following colors represents the wavelength of light with the most energy?

Violet - (shorter wavelengths have more energy)

Match the terms and symbols used to describe light with their definitions.

Visible spectrum - The kind of light our eyes can see Wavelength - The distance between crests in a light wave Frequency - The number of wave crests that pass a point in some time interval V - Symbol used for frequency in equations Symbol used for frequency in equations A - Symbol used for wavelength in equations Symbol used for wavelength in equations

Which property of light determines how much energy electromagnetic radiation carries?

Wavelength - (Because it is mathematically related to wavelength, frequency also indicates the energy of electromagnetic radiation)

Match the colors to the stars of the appropriate temperature

Whitish Red - Betelgeuse, temperature = 3,500 K Whitish Yellow - the Sun, temperature = 5,800 K Whitish Blue - Rigel, temperature = 11,000 K

What is the name of the following physical law: As an object's temperature increases, the object radiates light more strongly at shorter wavelengths.

Wien's law

The high energy of which kind of electromagnetic radiation allows it to penetrate the soft tissues of your body?

X rays

What kind of electromagnetic radiation has a shorter wavelength than visible and ultraviolet light?

X rays - (their shorter wavelength indicates they carry higher energy than visible and ultraviolet light)

The Kelvin temperature scale is used in virtually every physical science because in this scale, ____.

a body's temperature is directly related to its energy content

Each kind of atom has ____

a unique number of protons in the nucleus a different set of energy levels from any other kind of atom

If an atom has an electron in the ground state, it may ___ a photon with exactly enough energy to move the electron up to a higher level. When this happens, the atom is in an ___ state

absorb; excited

The diagram shows electron orbitals for an atom. Arrow A shows what happens when an atom ___ (emits or absorbs) light. Arrow B shows what happens when an atom ___(emits or absorbs) light.

absorbs; emits

When an atom ____ a photon, an electron moves to an upper orbital and the atom gains energy; when an atom ____ a photon, an electron moves to a lower orbital and the atom loses energy.

absorbs; emits

If you observe light from the extremely hot surface of a star after it passes through the less hot atmosphere of the star, then you will see a(n) ___ spectrum.

absorption-line

Planck's constant, h, describes the fundamental relationship between _____ and _______.

energy; wavelength

When an atom gains energy, the electron moves to a higher orbital, and the atom is said to be ___

excited

Electrons can only exist around the nucleus at certain allowed distances, which means the distances are ___ Each specific allowed distance is called a(n) ___

fixed; orbital

The ____ is the number of wave crests that pass a given point per second. It is measured in units of ''waves per second," also called___

frequency; hertz

Look at the electron orbital diagram. Which electronic transition would result in the atom emitting a photon with highest energy?

from level 4 to level 2 - (emitting energy requires the electron to drop to a lower level. The larger the drop, the more energy that is released)

If photon A has a wavelength twice as long as photon B, then photon A's frequency is ____.

half that of photon B - (wavelength and frequency are inversely proportional)

According to the _____, when an atom "loses energy," the energy is not actually lost but is changed into another form, usually a(n) _____.

law of conservation of energy; electromagnetic wave (photon)

Infrared radiation have wavelengths that are ___ than the wavelengths of red light

longer

Using the equation λ × ν = c, which best describes a red photon compared to a blue photon? Red photons have ____.

longer wavelengths and lower frequencies

Match the ways in which the attraction between a nucleus and an electron are similar to stretching and releasing a spring.

move an electron away from the nucleus - stretch a spring move an electron toward the nucleus - release a stretched spring

Select the two answers to complete this sentence: Electrons have ____ electric charge and are ____ the nucleus in an atom.

negative attracted to

In order to produce an absorption-line spectrum, light from a source emitting a continuous spectrum must ___

pass through a cool gas cloud

According to Wien's law, a hotter object emits light most strongly at ____ wavelengths and a cooler one emits most strongly at _____ wavelengths

shorter; longer - (Hotter objects emit mostly at shorter, bluer wavelengths. Shorter wavelengths are bluer wavelengths and are emitted more by hotter objects.Cooler objects emit mostly at longer, redder wavelengths.)

The technique used to observe and study a spectrum is called

spectroscopy

The ___ of light is measured in meters per second, while the ___ of a photon is measured in joules.

speed; energy

We know that cyanogen (CN) and carbon dioxide exist in gaseous form in comets because ____

these two molecules are detected in emission lines

Compared to visible light ____ has higher energy and ____ has lower energy.

ultraviolet light; infrared radiation

Infrared radiation ____

was discovered by Sir William Herschel is a form of heat radiation

The ___ model of light explains the focusing of light by lenses. The ___ model of light explains reflection of light off a mirror.

wave particle

When scientists use two different models to describe light, they are talking about the____ - ___duality

wave particle

The arrow "A" in the figure is measuring the ____ of the wave.

wavelength

The quantity commonly used to describe the color of light is ____ and it is usually measured in units of ____

wavelength; nanometers

Isaac Newton used a prism to disperse a beam of sunlight into the colors of the rainbow; he then used a second prism to recombine the colors back into ___ light

white

If an object were to reach a temperature of absolute zero (0 kelvin), the motion of molecules within it would be ___.

zero

How is electromagnetic radiation able to travel through empty space?

A disturbance in an electric field creates a disturbance in a magnetic field, which creates the next electric disturbance. - (Each disturbance creates the next one, allowing the wave to travel even without a medium to move through)

In the diagram of the visual spectrum, you would need to place a detector at position number ___to detect infrared and at position number ___ to detect ultraviolet light.

7; 1

Which spectrum is from an object emitting the largest number of red photons?

A - (This object looks blue, but it is so bright that it also emits lots of red light)

Select the statements below that are true for light waves.

The waves travel at about 300,000 kilometers per second in a vacuum. The waves can travel through air and water.

Why do you see more than one color of emission line in the spectrum of an interstellar hydrogen gas cloud? Select all that apply.

There are many atoms in the cloud, which don't all start out with their electrons in the same orbital. In some atoms, the electrons drop a much greater distance toward the nucleus than in others. The differences in energy between electron orbitals correspond to different colors of light.

Select all the statements that correctly describe how electrons orbiting an atom's nucleus are different from planets orbiting the Sun

Planets can orbit with any value of the semimajor axis; the distance of electrons at any moment is defined by their orbital and probability Planets follow elliptical orbits governed by Kepler's laws; electrons do not really orbit Electrons can be described as particles or waves; planets are best described as particles

Which kind of electromagnetic radiation can have wavelengths similar in length to a football field?

Radio waves

Arrange the types of electromagnetic waves in order from longest (top) to shortest (bottom) wavelength.

Radio waves Infrared light Visible light Ultraviolet light X rays Gamma rays

Select all the colors of light that are found in white light

Red Green Blue Yellow

Match the size of the wavelength of light with the color.

Red - long wavelength Yellow - intermediate wavelength Blue - short wavelength

Select all the correct statements about spectral line identification.

Some spectral lines are not in the visible part of the electromagnetic spectrum. Every hydrogen atom in a gas cloud emits the same pattern of spectral lines. Molecules can emit and absorb specific, unique colors of light.

What do scientists mean when they describe light as having a wave-particle duality?

That light is both a wave and a particle simultaneously - (light is both at the same time, but we normally can measure one aspect of it at a time)

Which of the objects below emit mostly visible blackbody radiation according to Wien's law?

The Sun

Select all the objects below that emit blackbody radiation according to Wien's law.

The Sun Earth The burner on an electric stove

What happens if you shine on an atom a photon whose energy does not equal the energy difference between two electron orbits?

The atom does not respond to the photon, and the electron does not move up or down. - (the atom can only absorb the photon if it has exactly enough energy to move an electron up to a higher level)

Select all the circumstances in which a hydrogen atom would be unable to absorb a photon.

The atom has lost its electron. The photon's energy does not match the energy difference between two electron orbitals.

The Sun has a temperature of 5800 K; according to Wien's law, the color it emits the most is bluish-green. Why does the Sun look yellow-white?

The human eye interprets light from extremely hot objects as white light - (Stars much hotter than the Sun appear white tinged with blue. Stars cooler that the Sun have a reddish tinge)

The strength of a spectral line is determined by what two properties?

The number of atoms or molecules radiating and their temperature

What determines the kind of chemical element an atom is?

The number of protons in the nucleus.