PHYS 1301 - Ch. 4 (LearnSmart & Connect).

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

- A grating. - A prism.

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

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

Match the terms with their definitions.

- Atomic number : Number of protons in nucleus. - Electron : Small, negatively charged particle orbiting nucleus. - Proton : Positively charged particles 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 coolers gases.

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

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

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

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

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

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

- Planck's constant, h. - it's wavelength, upside down y. - the speed of light, c.

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

- red : long wavelength. - yellow : intermediate wavelength. - blue : short wavelength.

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

1. 0 degrees Celsius. 2. 0 degrees Fahrenheit. 3. 0 degrees Kelvin.

Arrange the kinds of electromagnetic waves in order from highest (top) to lowest (bottom) energy.

1. Gamma rays. 2. X rays. 3. Ultraviolet light. 4. Visible light. 5. Infrared light. 6. Radio waves.

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.

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

1. Radio waves. 2. Infrared light. 3. Visible light. 4. Ultraviolet light. 5. X rays. 6. Gamma rays.

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.)

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.)

Electromagnetic radiation

A general term for any kind of electromagnetic wave.

Why does atomic hydrogen have a relatively simple emission specrum, 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.

Photon

A particle of visible light or other electromagnetic radiation.

Electromagnetic Wave

A wave consisting of alternating electric and magnetic energy. Ordinary visible light is an electromagnetic wave, and the wavelength determines the light's color.

Concentric rings are labeled from 1 to 4 from the center outwards. An arrow labeled A points from ring 1 to ring 3 and another labeled B from ring 4 to ring 1. Match the arrows showing an electron moving between orbitals to the correct descriptions.

Arrow A : similar to stretching a spring, atoms gain energy. Arrow B : similar to releasing a spring, atom emits energy.

Light

Electromagnetic energy.

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

The Sun. (The Sun emits mostly visible light.)

Electromagnetci spectrum

The assemblage of all wavelengths of electromagnetic radiation. The spectrum includes the following wavelengths, from long to short: radio, microwave, infrared, visible light, ultraviolet, X rays, and gamma rays.

What happens if you shine on an atom a photon whose energy does not equal the 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 elecron up toa higher level.)

Wavelength

The distance between wave crests. It determines the color of visible light and is usually denoted by the Greek letter A.

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 than the Sun have a reddish tinge.)

What determines the kind of chemical element an atom is?

The number of protons in the nucleus. (The number of protons also determines the chemical properties of the atom.)

Wave-particle duality

The theory that electromagnetic radiation may be treated as either a particle (photon) or an electromagnetic wave.

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

True. (The radio waves can be used to determine how much gas is in such a cloud.)

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.)

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

Violet. (Shorter wavelengths have more energy.)

Match each phenomenon of light with the model that best describes it.

Wave model : the color of light ; focusing of light by a lens. Particle model: reflection of light off a mirror ; brightness described as the number of photons observed.

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.)

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

Wein's law.

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

X rays. (This is why we call images of the insides of our bodies X rays!)

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 conent.

Ultraviolet

a portion of the electromagnetic with wavelengths shorter than those of visible light but longer than those of X rays. By convention, the ultraviolet region extends from about 10 nm to 400 nm.

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. (Electrons are negatively charged, and th protons in the nucleus are positively charged.)

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.

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.

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.

four.

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.

Concentric rings are labeled from 1 to 4 from the center outwards. An arrow labeled A points from ring 1 to ring 3 and another labeled B from ring 4 to ring 1. Look at the orbital diagram. Which electronic transiion would result in the atom emitting a photon with highest energy?

from level 4 to level 2. (Emitting energy requires the electron to drop 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 on 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].

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.

Infrared radiation have wavelengths that are _________ than the wavelengths of red light.

longer.

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

negative ; attracted to.

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

nucleus. (A nucleus can contain both protons and neutrons.)

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

pass through a cool gas cloud.

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

quantized ; orbital.

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

radio waves.

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.)

Frequency

the number of times per second that a wave vibrates.

visible spectrum

the part of the electromangnetic spectrum that we can see with our eyes. It consists of the familiar colors violet, blue, green, yellow, orange, and red, extending from about 400 nm to 700 nm.

Compared to visible light ___________ has higher energy and __________ has lower energy.

ultraviolet light ; infrared radiation.

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.

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.)

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 statements that correctly describe electron orbitals.

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

Select all the particles that make up the nucleus.

- Protons. - Neutrons.

Select all the correct statements about spectral line identification.

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

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

- The Sun. - Earth. - The burner on an electric stove.

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

- The atom has lost its electron. (An atom that has lost one or more electrons is said to be ionized. Hydrogen has only one, so without it, the atom cannot absorb or emit radiation.) - The photon's energy does not match the energy difference between two electron orbitals.

Multiple Select Question. Select all that are properties of light.

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

Select the statments below that are true for light waves.

- The waves travel at about 300,000 kilometers per second. - 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.

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. - ν : Symbol used for frequency in equations. - λ : Symbol used for wavelength in equations.

Select all of the following that correctly describe blackbodies.

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

Each kind of atom has _____________.

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

Infrared radiation ________.

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

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

- red. - yellow. - blue. - green.

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

- red. - yellow. - blue. - violet.

If you see a planet with a wavelength of maximum emission of 2.9x10^4nm, then its temperature will be ___________ K. (Enter a whole number. Use the version of Wien's law from the book.)

100.

Which atom described below is electrically neutral?

6 protons, 5 neutrons, 6 electrons. (An electrically neutral atom has equal numbers of protons [+1 charge] and electrons [-1 charge]. [Neutrons have no charge].)

In the diagram of the visual spectrum, you would need to place a detector at position number ___________ to detect ingrared and at position number _____________ to detect ultraviolet light.

7 ; one.

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. (The spectral lines of an element are used like fingerpritns to identify atoms.)

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

False. (According to Wien's law, hotter objects will emit at shorter wavelength, which are bluer colors.)

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

True. (The statement is true. For example, radio waves have much less energy than X rays or gamma rays.)

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

Ture. (Protons are positively charged, electrons negatively charged; and opposite charges attract.)

Infrared

a wavelength of electromagnetic radiation longer than visible light but shorter than radio waves. We cannot see these wavelengths with our eyes, but we can feel many of them as heat. The infrared wavelength region runs from about 700 nm to 1 nm.

If an atom has an electron in the ground state, it may __________ a photon with exactly enough energy to move the elecrtron 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.

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.

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 quantity commonly used to describe the color of light is _________, and it is usually measured in units of ___________.

wavelength ; nanometers.

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

wavelength.

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.

Match the colors to the stars of the appropriate temperature.

whitish red : Betelgeuse, temp. = 3,500 K. whitish yellow : the Sun, temp. = 5,800 K. whitish blue : Rigel, temp. = 11,000 K.

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.)

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

zero.

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.)