Mastering Astronomy Chapter 5 review questions

Choose the correct definition of a molecule.

A molecule is a group of two or more atoms bound together.

Which type is the Sun's visible-light spectrum, and why?

An absorption line spectrum. Relatively thin photosphere of the Sun absorbs the specific wavelength from the light emitted from the hot and dense interior of the Sun.

Choose the correct definition of an atom's atomic mass number.

An atom's atomic mass number is the number of protons plus the number of neutrons.

Choose the correct definition of an atom's atomic number.

An atom's atomic number is the number of protons it has in its nucleus.

The absorption line spectrum shows what we see when we look at a hot light source (such as a star or light bulb) directly behind a cooler cloud of gas. Suppose instead that we are looking at the gas cloud but the light source is off to the side instead of directly behind it. In that case, the spectrum would __________.

Be an emission line spectrum

Suppose we obtain a single, detailed (high-resolution) spectrum of a star located many light-years away. What can we learn about the star? Sort each of the following characteristics of a star into the correct bin based on whether we can or cannot learn it from the single spectrum.

CAN LEARN-surface temperature-speed toward or away from us-chemical composition (surface)CANNOT LEARN-mass-distance-interior temperature-size (diameter)-speed across our line of sight

Suppose we want to know what the Sun is made of. What should we do?

Compare the wavelengths of lines in the Sun's spectrum to the wavelengths of lines produced by chemical elements in the laboratory.

Why do dishes that aren't themselves heated by the microwave oven sometimes still get hot when you heat food on them? (Note: It's not a good idea to put empty dishes in a microwave.)

Conduction from heated food heats the dish.

Q8) What is electrical charge? Will an electron and a proton attract or repel each other? How about two electrons? Explain.

Electrical charge is a fundamental property that describes how strongly an object will interact in electromagnetic fields. Protons and electrons would attract, but electrons and electrons would not attract.

KC 5.3) How is energy stored in atoms?

Electrons can exist at particular energy levels within an atom. Energy level transitions, in which an electron moves from one energy level to another, can occur only when the electron gains or loses just the right amount of energy.

Under what circumstances can energy level transitions occur?

Electrons can make a transition from one level to another by taking in or emitting a specific amount of energy. If too much or too little energy is offered, the electron cannot make the transition.

Q10) Describe the energy levels that we find for electrons in atoms. Under what circumstances can energy level transitions occur?

Electrons have quantized energy levels in all atoms, not just in hydrogen. Quantized means that they are sudden changes with no in-between level. Energy level transitions can occur only when an electron gains or loses the exact amount of energy that separates two energy levels.

Q2) What are the four major ways light and matter can interact? Give an example of each from everyday life.

Emission ex) A light bulb emits visible light; the energy of the light comes from electrical potential energy supplied to the light bulb. Absorption ex) When you place your hand near an incandescent light bulb, your hand absorbs some of the light, and this absorbed energy warms your hand. Transmission ex) Some forms of matter, such as glass or air, transmit light, allowing it to pass through. Reflection/ scattering ex) Light can bounce off matter, leading to what we call reflection when the bouncing is all in the same general direction or scattering when the bouncing is more random

KC 5.4) How does light tell us what things are made of?

Emission lines or absorption lines occur only at specific wavelengths that correspond to particular energy level transitions in atoms or molecules. Every kind of atom, ion, and molecule produces a unique set of spectral lines, so we can determine composition by identifying these lines.

Q1) What is the difference between energy and power? What units do we use to measure power?

Energy is the ability to do work whereas power is the amount of work done in a given period of time. Units used to measure power: watts

Comte was proven wrong in his claim that we could never learn the composition of stars. What do we know today that Comte did not know when making his claim, and that makes it possible for us to learn the chemical compositions of stars?

Every chemical element produces a unique spectral fingerprint.

Q18) Because of their higher frequencies, x-rays must travel through space faster than radio waves.

False All light travels through space at the same speed of light

Q24) If you could view a spectrum of light reflecting off a blue sweatshirt, you'd find the entire rainbow of color (looking the same as a spectrum of white light).

False. You would see only blue coloring. Blue objects absorb all of the colors of the rainbow other than blue.

Q25) Galaxies that show redshifts must be red in color.

False. For distant galaxies, the light spectrum is wrong. The frequency lines of the spectrum are all too low. One possible explanation of the incorrect spectrum is that those stars and galaxies are moving away from us, and that the spectrum is shifted toward the red end of the color spectrumm because of the Doppler effect.

Q20) If you had x-ray vision, you could read this entire book without turning any pages.

False. If you were using x-ray vision, you would not be able to resolve the letters on individual pages.

Q21) Two isotopes of the element rubidium differ in their number of protons.

False. Isotopes of the same element must differ in the number of neutrons, not protons.

Q5) List the different forms of light in order from lowest to highest energy. Is the order the same from lowest to highest frequency? From shortest to longest wavelength? Explain.

From lowest to highest energy, the different forms of light are radio, microwave, infrared, visible, ultraviolet, X-rays, and gamma rays. The list would be the same if you listed them from lowest to highest frequency since the energy is directly proportional to the frequency. If you listed them by wavelength, the list would be reversed since the energy is inversely proportional to the wavelength.

Q13) How can we use emission or absorption lines to determine the chemical composition of a distant object?

Hydrogen emits and absorbs light at specific wavelengths, therefore if youre looking at a distant cloud that produces a certain spectrum (w/ certain absorption lines), you can know its made of hydrogen. Each chemical and its ions leave different "fingerprints."

KC 5.2) What is the electromagnetic spectrum?

In order of decreasing wavelength (increasing frequency and energy), the forms of light are radio waves, microwaves, infrared, visible light, ultraviolet, x-rays, and gamma rays.

How do the spectra of the different types of light bulbs compare?

Incandescent light bulbs emit generally continuous thermal spectra. CFLs and LEDs emit the light in the broad bands near specific wavelengths.

Why CFLs and LEDs can be much more energy efficient than incandescent bulbs?

Incandescent light bulbs emit most of consumed energy in infrared wavelengths. CFLs and LEDs transfer almost all consumed energy to visible light.

Q16) Describe each of the key features of the spectrum in Figure 5.25 and explain what it tells us about the object.

Key features of the martian spectrum include the dashed line of the continuous spectrum (caused by the Sun's reflected light), the high intensity of the scattered red light (tells us the chemical composition of Mars-its blue), the peak in the thermal radiation is in the infrared (tells us its much cooler than the Sun), emission lines in the UV (tells us Mars' atmosphere contains hot gas at high altitudes), absorption lines (tells us about CO2 in the atmosphere), and the Doppler Effect (towards red means Mars is moving away and towards Blue means towards us)

KC 5.1) How do we experience light?

Light carries radiative energy that it can exchange with matter. Power is the rate of energy transfer, measured in watts: 1 watt= 1 joules/s. The colors of light contain a great deal of information about the matter with which it has interacted.

Emission

Light comes from your computer screen. Light comes from a light bulb.

Why do we say that light is an electromagnetic wave? What is the relationship among wavelength, frequency, and speed for light?

Light is a vibration of electric and magnetic fields. ν=cλν=cλ.

KC 5.2) What is light?

Light is an electromagnetic wave, but it also comes in individual "pieces" called photons. Each photon has a precise wavelength, frequency, and energy: The shorter the wavelength, the higher the frequency and energy.

KC 5.1) How do light and matter interact?

Matter can emit, absorb, transmit, or reflect (or scatter) light.

Why doesn't a microwave oven make a plastic dish get hot?

Microwave ovens are tuned to emit frequencies absorbed by water molecules, not by a plastic dish.

KC 5.4) How does light tell us the temperatures of planets and stars?

Objects such as planets and stars produce thermal radiation spectra, the most common type of continuous spectra. We can determine temperature from these spectra because hotter objects emit more total radiation per unit area and emit photons with a higher average energy.

Which of the following procedures would allow you to make a spectrum of the Sun similar to the one shown, though with less detail?

Pass a narrow beam of sunlight through a prism.

Why do some clay dishes get hot in the microwave?

Some clay dishes contain some water inside them.

Q14)Describe two ways in which the thermal radiation spectrum of an 8000 K star would differ from that of a 4000 K star.

The 8000K star would 1. have a shorter wavelength of peak emission, and 2. would emit more light at all wavelengths

Q15) Describe the Doppler effect for light and what we can learn from it. What does it mean to say that radio waves are blueshifted? Why does the Doppler effect widen the spectral lines of rotating objects?

The Doppler Effect is when the wavelengths of spectral lines are slightly shifted depending on the velocity of the light and whether it is moving towards or away from us as it orbits the Sun. Blue-shifted (closer together) radio waves means the object is moving towards us. The Doppler effect widens the spectral lines of rotating objects because the wavelengths changes from blue or red. Blue-shifted, red-shifted, and non-shifted photons mix together to get how its rotating.

KC 5.4) How does light tell us the speed of a distant object?

The Doppler effect tells us how fast an object is moving toward or away from us. Spectral lines are shifted to shorter wavelengths (a blueshift) in objects moving toward us and to longer wavelengths (a redshift) in objects moving away from us.

Which of the following best describes why the Sun's spectrum contains black lines over an underlying rainbow?

The Sun's hot interior produces a continuous rainbow of color, but cooler gas at the surface absorbs light at particular wavelengths.

The "extraordinary" part of Comte's claim was his statement that we could never learn the composition of stars. Which of the following best summarizes the key lesson we should learn from the fact that his claim was ultimately proven wrong?

The advance of science and technology may someday provide ways to answer questions that seem unanswerable today.

KC 5.3) What are the phases of matter?

The appearance of matter depends on its phase: solid, liquid, or gas. Some gas always vaporizes from the solid or liquid phases; solids sublimate into gas and liquids evaporate into gas. At very high temperatures, molecular dissociation breaks up molecules and ionization strips electrons from atoms; an ionized gas is called a plasma.

Q6) Briefly describe the structure and size of an atom. How big is the nucleus in comparison to the entire atom?

The atom is made of three different parts: the Electrons (negative charge), protons (positive charge), and the neutrons (no charge). The protons and neutrons make up the nucleus (the center of the atom) and the electrons fly around the nucleus. The nucleus (in comparison to the entirety of the atom) is the smallest part but holds the most mass. What determines an atom's

KC 5.4) What are the three basic types of spectra?

There are three basic types of spectra: a continuous spectrum, which looks like a rainbow of light; an absorption line spectrum, in which specific colors are missing from the rainbow; and an emission line spectrum, in which we see light only with specific colors against a black background.

Q26) If a distant galaxy has a substantial redshift (as viewed from Earth), then anyone living in that galaxy would see a substantial redshift in a spectrum of the Milky Way Galaxy.

This statement makes sense. The redshift means that we see the galaxy moving away from us, so observers in that galaxy must also see us moving away from them—which means they see us redshifted as well.

Q11) How do we convert a spectrum shown as a band of light (like a rainbow) into a graph of the spectrum?

Through spectroscopy. And then changing them from showing only visible light to showing the amount of radiation, or intensity, at each wavelength.

Q19) If you could see infrared light, you would see a glow from the backs of your eyelids when you closed your eyes.

True Because your eyelids are warm and emit infrared radiation

Q17) The walls of my room are transparent to radio waves.

True Radio waves pass through most walls, which is why you can receive radio broadcasts and cell phone calls inside a house

Q22) A "white hot" object is hotter than a "red hot" object.

True. An object must emit a red color from heat before it can emit a white color, because white is all of the colors combined.

Q23) If the Sun's surface became much hotter (while the Sun's size remained the same), the Sun would emit more ultraviolet light but less visible light than it currently emits.

True. When heat increases, so does the frequency and energy of the wavelengths. Because of this, some visible light would be converted to ultraviolet light.

Choose the correct conditions, under which two atoms are different isotopes of the same element.

Two atoms having the same number of protons and different numbers of neutrons.

Absorption

Visible light does not pass through a black wall. Blue light hits a red sweatshirt.

Transmission

Visible light meets clear glass. Cell phone signals pass through walls.

Q9) Describe the phase changes of water as you heat it, starting from its solid phase, ice. What happens at very high temperatures? What is a plasma?

Water will be in a solid from as ice and as it heats up it becomes a liquid form known as water. When it obtains enough energy it will become its gaseous form through a process called evaporation. A plasma is a type of hot gas in which atoms have ionized. Because a plasma contains many charged particles, its interactions with light are different from those of a gas consisting of neutral atoms, which is one reason that plasma is sometimes referred to as "the fourth phase of matter".

Study the graph of the intensity of light versus wavelength for continuous spectra, observing how it changes with the temperature of the light bulb. Recall that one of the laws of thermal radiation states that a higher-temperature object emits photons with higher average energy (Wien's law). This law is illustrated by the fact that for a higher temperature object, the graph peaks at __________.

a Shorter Wavelength

We see __________ spectrum when we look a dense hot object emitting light.

a continuous

Q29) Radio waves are (a) a form of sound. (b) a form of light. (c) a type of spectrum.

a form of light

Q33) If you heat a rock until it glows, its spectrum will be (a) a thermal radiation spectrum. (b) an absorption line spectrum. (c) an emission line spectrum.

a thermal radiation spectrum.

We see ____________ spectrum when we look through a cloud of gas at a dense hot object emitting light.

an absorption line

What type of visible light spectrum does the Sun produce?

an absorption line spectrum

.We see _________ spectrum when we look at a cloud of thin and hot gas.

an emission line spectrum

Q7) Define atomic number and atomic mass number. Under what conditions are two atoms different isotopes of the same element? What is a molecule?

atomic number: the number of protons it has in its nucleus. atomic mass number: the number of protons plus the number of neutrons. Isotopes occur when there is the same # of protons, but a different # of neutrons (giving it a different mass by same atomic number)A molecule is when atoms of the same element combine.

The set of spectral lines that we see in a star's spectrum depends on the star's:

chemical composition.

Q35) Compared to the Sun, a star whose spectrum peaks in the infrared is (a) cooler. (b) hotter. (c) larger.

cooler

Q31) Some nitrogen atoms have seven neutrons and some have eight neutrons; these two forms of nitrogen are (a) ions of each other. (b) phases of each other. (c) isotopes of each other.

isotopes of eachother.

In the illustration of the solar spectrum, the upper left portion of the spectrum shows the __________ visible light.

lowest frequency

Click "show" for the emission line spectrum, then click "choose gases" and study the emission line spectrum for neon. The neon "OPEN" sign appears reddish-orange because __________.

neon atoms emit many more yellow and red photons than blue and violet photons

Rank the forms of light from left to right in order of increasing energy. To rank items as equivalent, overlap them.

radio waves infrared visible light ultraviolet X rays gamma rays

Rank the forms of light from left to right in order of increasing frequency. To rank items as equivalent, overlap them.

radio waves infrared visible light ultraviolet X rays gamma rays

36) A spectral line that appears at a wavelength of 321 nm in the laboratory appears at a wavelength of 328 nm in the spectrum of a distant object. We say that the object's spectrum is (a) redshifted. (b) blueshifted. (c) whiteshifted.

redshifted.

Q34) The set of spectral lines that we see in a star's spectrum depends on the star's (a) interior temperature. (b) chemical composition. (c) rotation rate.

rotation rate.

Q4) What is a photon? In what way is a photon like a particle? In what way is it like a wave?

"pieces," or single units of light, that have properties of particles AND waves. It's like a particle b/c they can be counted individually and can hit surfaces one at a time. And they're like waves because each one is characterized by the same properties as waves (like wavelength and frequency).

Q27) Why is a sunflower yellow? (a) It emits yellow light. (b) It absorbs yellow light. (c) It reflects yellow light.

C) It reflects yellow light

KC 5.3) What is the structure of matter?

Ordinary matter is made of atoms, which are made of protons, neutrons, and electrons. Atoms of different chemical elements have different numbers of protons. Isotopes of a particular chemical element all have the same number of protons but different numbers of neutrons. Molecules are made from two or more atoms.

Would the order of the ranking for the different forms of light listed in Part A be different if you were ranking the frequency of the different forms of light (lowest to highest, left to right)? What if the ranking is done for the wavelengths of the different forms of light (shortest to longest, left to right)?

The ranking by frequency would have the same order, since energy is directly proportional to frequency. The ranking by wavelength would have the opposite order, because frequency and wavelength are inversely related.

What do we mean when we say that energy levels are quantized in atoms?

We mean that the electrons can have only discrete values of electrical potential energy in atoms.

Q3) Why do we say that light is an electromagnetic wave? Describe the relationship among wavelength, frequency, and speed for light.

We say that light is an electromagnetic wave because light is an oscillation of electric and magnetic fields. Frequency = speed of light / wavelength

Reflection or scattering

White light hits a white piece of paper. Red light hits a red sweatshirt.

Q32) Ionization is the process by which (a) electrons escape from atoms. (b) liquid material enters the gas phase. (c) molecules break apart into individual atoms.

electrons escape from atoms

We divide the electromagnetic spectrum into six major categories of light, listed below. Rank these forms of light from left to right in order of increasing wavelength. To rank items as equivalent, overlap them.

gamma rays X rays ultraviolet visible light infrared radio waves

List the different forms of light in order from highest to lowest energy.

gamma rays, X-rays, ultraviolet radiation, visible light, infrared radiation, and radio waves.

Q28) Compared to red light, blue light has higher frequency and (a) higher energy and shorter wavelength. (b) higher energy and longer wavelength. (c) lower energy and shorter wavelength.

higher energy and shorter wavelength

Rank the forms of light from left to right in order of increasing speed. To rank items as equivalent, overlap them.

infrared, visible light, gamma rays, ultraviolet, radio waves, X rays ALL THE SAME SPEED

Notice that the Sun's spectrum appears brightest (or most intense) in the yellow-green region. This fact tells us __________.

the approximate temperature of the Sun's surface

Q30) Compared to an atom as a whole, an atomic nucleus is (a) very tiny but has most of the mass. (b) quite large and has most of the mass. (c) very tiny and has very little mass.

very tiny but has most of the mass