Deck 5: The Nature of Light

Question 1

No matter how close or how far Galileo was from his assistant, he always measured roughly the same time in performing the lantern experiment. Just what time was Galileo measuring?

A)the time for light to travel from his assistant to himself
B)the round-trip time for light to travel between Galileo and his assistant
C)his own reaction time-that is, the time for him to open his shutter after observing his assistant's light
D)the combined reaction time of Galileo and his assistant

Answer 1

D

Question 2

The first experiment in which the speed of light was measured precisely involved:

A)timing eclipses of Jupiter's satellites, which appeared to occur later when Earth was farther from Jupiter.
B)measuring how long it took the light from stars located at different distances to reach Earth.
C)reflecting light from a mirror rotating at a known speed and measuring the angle of deflection of the light beam.
D)opening a shutter on a lantern on a hilltop and measuring the time taken for light from an assistant's shuttered lantern to return.

Answer 2

C

Question 3

The first experiment to measure the speed of light accurately was made by the:

A)French physicists, Fizeau and Foucault.
B)Danish astronomer, Rømer.
C)Italian scientist, Galileo.
D)German/American physicist, Einstein.

Answer 3

A

Question 4

The speed of light:

A)was first accurately determined by Galileo in an experiment involving lanterns and shutters.
B)can be determined by observing the motions of the moons of Jupiter.
C)was not determined until the advent of lasers in 1960.
D)is too high to measure and consequently is still unknown.

Question 5

Rømer calculated the speed of light by observing the large moons of Jupiter being eclipsed by Jupiter while that planet was at opposition and while it was at superior conjunction. How large is the difference in the Jupiter-Earth distance when Jupiter is at opposition and when it is at superior conjunction?

A)1 au
B)2 au
C)1 ly
D)0 au

Question 6

Earth is about 150,000,000 km from the Sun. How long did it take light to cross Earth's orbit in Rømer's experimental determination of the speed of light?

A)about 8 seconds
B)about 16 seconds
C)about 8 minutes
D)about 16 minutes

Question 7

Assuming that Uranus was at opposition to Earth when Voyager II sent back its historic (and magnificent) pictures from Uranus in January 1986, how long did those signals take to arrive after transmission by Voyager? The average distance of Neptune from the Sun is about $2871 \times 10^{6} \mathrm{~km}$ .

A)9066.7 min
B)151.1 hrs
C)5 hrs 2 min
D)2 hrs 31 min

Question 8

As of 2018, Voyager 1 is in interstellar space, about 13 billion miles from Earth. How long does it take data transmitted by Voyager 1 to reach the Deep Space Network on Earth?

A)about 90 min
B)about 19 hrs
C)3 days
D)2 weeks

Question 9

White light passes through a prism and separates into a spectrum of colors. A second prism is placed so that only the green light from the first prism falls upon it. After passing through this second prism the light will be:

A)white.
B)green.
C)ultraviolet.
D)infrared.

Question 10

The rear brake lights on a car emit white light but are covered with plastic that allows only pure red light to pass through. What color of plastic would the red light have to pass through in order to emerge as green light?

A)white
B)green
C)blue
D)There is no color plastic that will turn pure red light into green.

Question 11

Light of a single wavelength falls on a screen with two narrow, closely spaced slits. On a second screen, a short distance beyond the first:

A)nothing will be seen since light cannot pass through narrow slits.
B)two bright lines corresponding to the two slits will be observed.
C)a totally random mixture of light and dark will be seen.
D)a series of bright lines with dark spaces in between will be seen.

Question 12

Around 1801, Thomas Young in England showed that light behaves as a wave by:

A)deriving a set of mathematical equations that described electromagnetic waves that could have different wavelengths.
B)shining light through two closely spaced slits and observing the resulting pattern of light on a white screen.
C)reflecting light from a rotating mirror and measuring the deflection in different directions.
D)shining light through a glass prism and observing the resulting pattern of colors on a white screen.

Question 13

Who was the first person to suggest that light is made of particles?

A)Isaac Newton
B)Christiaan Huygens
C)Thomas Young
D)James Clerk Maxwell

Question 14

In order of increasing frequency, some of the colors that the visible spectrum contains are:

A)blue, red, and yellow.
B)red, blue, and yellow.
C)red, yellow, and blue.
D)blue, yellow, and red.

Question 15

The diameter of your finger is 1 or 2 cm. What type of electromagnetic wave has a wavelength this size?

A)ultraviolet
B)visible
C)microwave
D)radio

Question 16

How does the frequency at the red end of the visible spectrum compare with the frequency at the blue-violet end of the visible spectrum?

A)It is about twice as big.
B)It is about half as big.
C)It is several orders of magnitude smaller.
D)It is several orders of magnitude larger.

Question 17

How does the wavelength at the red end of the visible spectrum compare with the wavelength at the blue-violet end of the visible spectrum?

A)It is about twice as big.
B)It is about half as big.
C)It is several orders of magnitude smaller.
D)It is several orders of magnitude larger.

Question 18

What is the wavelength of radio waves from the FM radio station KTYD, which operates at the frequency 99.9 MHz?

A)99.9 m
B)3.0 m
C)300 m
D)33.3 m

Question 19

Choose the correct sequence of electromagnetic radiations, in order of increasing wavelengths.

A)radio, IR, visible, UV
B)UV, visible, radio, IR
C)UV, visible, IR, radio
D)visible, UV, IR, radio

Question 20

In terms of wavelengths, gamma rays are:

A)shorter than x rays.
B)between radio and infrared waves.
C)between x rays and ultraviolet waves.
D)longer than visible light.

Question 21

What is one fundamental difference between x rays and radio waves?

A)They always come from different sources.
B)Their wavelengths are very different.
C)Radio waves are always wavelike, while x rays always behave like particles.
D)Their speeds in outer space are different.

Question 22

What is the wavelength of electromagnetic radiation whose frequency is 10⁶ cycles per second (10⁶ Hz or 1000 kHz, the frequency of ordinary AM radio)?

A)3 mm
B)3 cm
C)3 m
D)300 m

Question 23

In a radio wave transmitter (such as that used by a radio or TV station), when the frequency of the signals is increased, the:

A)wavelength is decreased.
B)speed of transmission of the waves is increased.
C)wavelength and speed of transmission both increase.
D)wavelength remains constant.

Question 24

Which one of these scientists was the last to perform his investigation of electromagnetic radiation?

A)Newton (the prism experiment)
B)Hertz (production of radio waves)
C)Young (two-slit interference experiment)
D)Huygens (wave theory of light)

Question 25

The temperature of a gas cloud in space is directly related to and representative of the:

A)number of atomic collisions per second within the cloud.
B)average speed of its atoms.
C)density of the cloud.
D)color of the cloud.

Question 26

To what physical parameter is the temperature of a thin gas most closely related?

A)average number of collisions per second between molecules
B)pressure of the gas
C)average speed of the molecules
D)mean mass per unit volume, or density, of the gas

Question 27

At absolute zero temperature, which of the following conditions holds?

A)Electrons stop moving around the nuclei of atoms.
B)The motion of atoms ceases.
C)Electrons in all atoms move to their ground states.
D)The motion of atoms becomes the minimum possible (but not zero).

Question 28

An example of an object that emits no radiation at all is:

A)an object with the temperature of outer space.
B)a blackbody.
C)an object made of ice.
D)an object at a temperature of 0 K.

Question 29

Two physicists, one in Australia, the other in the United States, find that each has constructed an ideal blackbody in the laboratory. The two blackbodies are made from very different materials. Without conducting tests, they know that the radiation emitted by these two objects will be:

A)different because the amount of light falling on them is likely to be different in the two laboratories.
B)identical to each other if the blackbodies have the same size, even if their temperatures are different.
C)different from each other because of the difference in materials.
D)identical to each other if the blackbodies are at the same temperature but not otherwise.

Question 30

Figure 5-12 in Universe, 11th ed., shows that a blackbody with a temperature of 3000 K emits radiation that peaks at a wavelength much longer than wavelengths in the visible part of the spectrum. This means that:
​ ​

A)the object is not visible but might be detected with equipment sensitive to nonvisible radiation.
B)the object, like all blackbodies, emits no radiation.
C)the object emits visible radiation, but not as intensely as at longer wavelengths.
D)no visible radiation is emitted, but visible radiation would be emitted if the temperature of the object were increased.

Question 31

Compare the spectrum emitted from a blackbody at 12,000 K and at 3000 K, using Figure 5-12 of Universe, 11th ed. Where in the spectrum does the object emit more radiation when it is cooler than when it is warmer?
​
​

A)ultraviolet
B)visible
C)infrared
D)nowhere

Question 32

Wien's law, relating the peak wavelength λ_max of light emitted by a dense object to its temperature T, can be represented by:

A)λ_max = constant × T ⁴.
B)λ_max T = constant.
C)λ_max = constant/T ².
D)λ_max/T = constant.

Question 33

As a new star evolves from cool dust and gas to a hot star, the peak wavelength of its spectrum of electromagnetic radiation:

A)changes from the ultraviolet to the visible range.
B)changes from the infrared to the visible wavelengths.
C)increases from the visible to infrared wavelengths.
D)remains the same.

Question 34

Using Wien's law, which relates the peak wavelength λ_max, (1 μm = 10^-6 m) emitted by a body to its temperature T, what is the peak wavelength of electromagnetic radiation emitted by a piece of iron that is just melting (1538°C)? (See Box 5-2 and Figure 5-7 of Universe, 11th ed.)

A)16 μm, intermediate infrared
B)1.89 μm, near infrared
C)1.04 μm, very near infrared
D)1.6 μm, near infrared

Question 35

You are asked to design a detection system for human beings (or animals) in darkness, using infrared detection. If human beings are at a temperature of about 310 K, what would need to be the wavelength of peak sensitivity of your equipment or cameras (1 μm = 10^-6 m)? (Hint: Use Wien's law.)

A)9.35 μm
B)0.935 μm
C)0.00094 μm or 0.94 nm
D)90 μm

Question 36

Using Wien's law, what is the approximate peak wavelength of radiation emitted by (live) human beings, who are (normally) at a temperature of about 310 K (1 μm = 10^-6 m)?

A)9.4 μm
B)3.1 μm
C)94 μm
D)0.94 μm

Question 37

The wavelength of the peak in the Sun's output spectrum is about 500 nm. If the Sun's surface temperature doubled, what would this peak wavelength become?

A)250 nm
B)500 nm
C)750 nm
D)1000 nm

Question 38

An astronomer wants to know whether a particular star has a greater surface temperature than the Sun. What does she need to know about this star to determine its temperature?

A)the wavelength at the peak of its spectrum
B)its distance from the Sun
C)its size
D)its age

Question 39

The total energy flux F of radiation emitted per unit area by a blackbody (e.g., star) is related to its temperature T and a constant σ by which equation?

A)F = σT ⁴
B)FT ⁴ = σ
C)F ⁴ = σT
D)F = σ /T

Question 40

When a solid body is heated to a temperature T, the total radiated energy flux F from this body per second per unit area is given by (where σ is a constant):

A)F = σT.
B)F = σ/T ².
C)F = σT ⁴.
D)FT = σ.

Question 41

The laws governing the energy flux F and wavelength of maximum intensity λ_max of emitted radiation from a hot, dense body whose temperature is T are given by (where σ and a are constants):

A)F = σT ², λ_max T = a.
B)F = σT ⁴, λ_max T = a.
C)F = σT, λ_max = a/T ⁴.
D)F = σT ⁴, λ_max = aT.

Question 42

A piece of iron is heated from 400 K to 800 K (127°C to 527°C). By what factor will the total energy per second emitted by this iron increase?

A)2
B)296.5
C)4
D)16

Question 43

The energy flux arriving at Earth from the Sun is known as the solar constant and has a value of 1.37 × 10³ watts per square meter. Assuming that the atmosphere absorbs 50% of the energy and that a 5-m² roof collector is available to collect energy with a 30% efficiency, how much of this solar energy would then be available for use in the house for water or house heating, etc.? (1 KW = 1 kilowatt = 1000 W)

A)about 1 KW
B)about 46 KW
C)about 1 W
D)about 10 KW

Question 44

The Stefan-Boltzmann law relating energy per unit area F emitted by an object to its temperature T, F = σT ⁴, is obeyed ideally by what type of object?

A)only hot gases, whose atoms emit and absorb only specific colors (e.g., neon tubes)
B)all objects, whatever their color or reflective properties
C)a red-colored object that absorbs blue light but reflects red light
D)a blackbody, a perfect absorber and emitter of energy at all wavelengths

Question 45

The radius of the Sun is about 1/200 of an astronomical unit. What happens to the flux of solar energy as it travels from the Sun's surface to Earth?

A)It remains constant.
B)It increases by a factor of 200.
C)It decreases by a factor of 200.
D)It decreases by a factor of (200)² = 40,000.

Question 46

Can a cooler object ever emit more radiation than a warmer object?

A)No.
B)Yes, if the two have the same surface area.
C)Yes, if the cooler object has an area A_cooler that meets the requirement T_cooler A_cooler > T_hot A_hot.
D)Yes, if the cooler object has an area A_cooler that meets the requirement (T_cooler )⁴A_cooler > (T_hot )⁴ A_hot.

Question 47

The Sun's surface has a temperature of 5800 K. What will be the peak wavelength of the spectrum of a star that emits twice the Sun's flux of energy?

A)2.1 × 10^-7 m
B)4.0 × 10^-7 m
C)5.0 × 10^-7 m
D)1.0 × 10^-6 m

Question 48

Proxima Centauri, our Sun's nearest stellar neighbor, has a surface temperature of about 3300 K. At what wavelength does Proxima Centauri emit its most intense radiation?

A)about 200 nm
B)about 400 nm
C)about 600 nm
D)about 900 nm

Question 49

Proxima Centauri, our Sun's nearest stellar neighbor, has a surface temperature of about 3300 K. What color will this star appear to the naked eye?

A)red
B)yellow
C)white
D)blue

Question 50

In its interaction with matter, light behaves:

A)only as waves.
B)alternatively as particles or as waves, switching its properties about once every second.
C)as both waves and particles, depending on the type of interaction.
D)only as small particles, photons.

Question 51

A photon is:

A)a positively charged particle in the atomic nucleus.
B)an element with a high atomic number.
C)a particle that orbits the nucleus of an atom.
D)a bundle of pure energy.

Question 52

In comparing photons of different wavelengths, we find that the energy carried by a photon:

A)increases as the wavelength increases up to a wavelength equal to λ_max, then decreases again.
B)does not depend on its wavelength.
C)is larger if the wavelength is shorter.
D)is larger if the wavelength is longer.

Question 53

The energy of a photon of x rays, compared to the energy of a photon of visible light, is:

A)about the same.
B)much lower.
C)variable and can be higher or lower under certain circumstances and in certain positions in the universe.
D)much higher.

Question 54

The energy E of a photon or quantum of electromagnetic radiation is related to the wavelength λ of the radiation by what relation (h = Planck's constant)?

A)E = hc/λ
B)E = hλ
C)E = hcλ
D)E = h/cλ

Question 55

The human eye is most sensitive to light with a wavelength near 550 nm. To what photon energy is the human eye most sensitive?

A)2.49 eV
B)3.61 × 10^-19 eV
C)2.25 eV
D)1.83 eV

Question 56

What is the energy in eV of a photon with the wavelength of Lyman Lα at 121.5 nm in the ultraviolet range?

A)1030 eV
B)1.51 × 10^-4 eV
C)1.02 × 10^-8 eV
D)10.2 eV

Question 57

What is the wavelength of the radiation whose photons have 1 eV of energy?

A)8.1 × 10^-4 nm
B)1240 nm in the infrared range
C)1.24 × 10^-6 nm, gamma rays
D)124 nm in the ultraviolet range

Question 58

What is the energy in electron volts of a photon whose wavelength is the diameter of a typical atom, about 0.1 nm?

A)12.4 keV, or 12,400 eV
B)1.24 × 10^-7 eV
C)1.24 keV, or 1240 eV
D)8.061 MeV, or 8,061,000 eV

Question 59

The dark absorption lines in the solar spectrum are caused by absorption:

A)of sunlight in a layer of pure hydrogen gas overlying the solar surface.
B)of sunlight in a cooler layer of gas overlying the hot solar surface.
C)entirely by atoms and molecules in Earth's cool atmosphere.
D)of sunlight in a hotter layer of gas overlying the cooler solar surface.

Question 60

If light from a hot, dense star is viewed through a cool cloud of gas (See Figure 5-17 of Universe, 11th ed.):
​
​

A)the spectrum of the star will still be seen unchanged because the gas cloud is cool.
B)only specific wavelengths of light will be removed from the spectrum.
C)the whole spectrum will be reduced in intensity.
D)the atoms of the gas cloud will add energy to the overall spectrum, producing emission lines at specific wavelengths.

Question 61

During a dust storm the Sun often appears to redden. This means that the particles of dust:

A)are equal in size to the wavelength of red light.
B)are larger than the wavelengths of visible light.
C)are smaller than the wavelengths of visible light.
D)must be red in color.

Question 62

You are looking at a glowing field of hot lava from a satellite high above Earth's atmosphere. Hot lava emits most of its radiation in the infrared, and Earth's atmosphere is not completely transparent to infrared. What kind of spectrum will you see?

A)a flat spectrum, equally intense at short and long wavelengths
B)an emission spectrum
C)an absorption spectrum
D)no spectrum at any wavelength

Question 63

The overall diameter of a typical atom is about:

A)10^-7 m, or 10² nm.
B)10^-5 m, or 10⁴ nm.
C)10^-14 m, or 10^-5 nm.
D)10^-10 m, or 0.1 nm.

Question 64

The typical size of an atom is:

A)10^-6 m.
B)10^-8 m.
C)1 m.
D)10^-10 m.

Question 65

The mass of a proton is:

A)about twice as large as that of an electron.
B)almost 2000 times greater than that of an electron.
C)about the same as that of an electron.
D)about 1/2000 as large as that of an electron.

Question 66

The majority of the naturally occurring elements in the periodic table that decay radioactively are:

A)arranged randomly throughout the table, because stability is largely independent of nuclear mass.
B)at the low-mass end of the table, since the nuclear mass is too small to maintain stability.
C)in the center of the table.
D)at the high-mass end of the table, since the large atomic nuclei are unstable.

Question 67

According to the arrangement of elements in the periodic table, which of the following elements would be expected to have chemical properties most similar to those of nitrogen, N, whose atomic number is 7?
​
​

A)oxygen (O, atomic number 8)
B)phosphorous (P, atomic number 15)
C)chlorine (Cl, atomic number 17)
D)carbon (C, atomic number 6)

Question 68

Isotopes of a particular element in the periodic table have which nuclear property in common?

A)same number of neutrons but different numbers of protons
B)same number of neutrons, but different numbers of protons and electrons
C)same total number of protons and neutrons
D)same number of protons but different numbers of neutrons

Question 69

How many neutrons are there in the nucleus of the isotope ¹⁸O of oxygen?

A)8
B)18
C)9
D)10

Question 70

How do the spectra of the two isotopes ¹H and ²H compare?

A)These isotopes each have one proton, which makes them both hydrogen, so they have identical spectra.
B)The wavelengths for the heavier isotope are very slightly longer than those for the lighter isotope.
C)The wavelengths for the heavier isotope are very slightly shorter than those for the lighter isotope.
D)Since the nuclei are different, the two spectra differ greatly.

Question 71

One atom of ¹³C has how many particles?

A)13: 6 protons, 1 neutron, 6 electrons
B)19: 6 protons, 7 neutrons, 6 electrons
C)20: 6 protons, 7 neutrons, 7 electrons
D)39: 13 protons, 13 neutrons, 13 electrons

Question 72

The specific sequence of spectral line series emitted by excited hydrogen atoms, in order of increasing wavelength range, is:

A)Balmer, Lyman, Paschen.
B)Lyman, Balmer, Paschen.
C)Lyman, Paschen, Balmer.
D)Paschen, Balmer, Lyman.

Question 73

The upward Lyman series transitions in hydrogen begin with electrons in the ground state (n = 1), which is the state of most hydrogen atoms. Yet the Balmer series was studied first and was the basis of the early attempts to explain the lines. This is because:

A)upward transitions never occur; only downward transitions occur.
B)the entire Balmer series is in the visible part of the spectrum.
C)the first few transitions (low n) in the Balmer series are in the visible.
D)the last few transitions (high n) in the Balmer series are in the visible.

Question 74

Compare two electron transitions in hydrogen: n = 3 → n = 1 and n = 2 → n = 1. Which produces the photon with the higher frequency?

A)n = 3 → n = 1
B)n = 2 → n = 1
C)The frequencies are the same.
D)It is not possible to determine the higher frequency without additional information.

Question 75

When a hydrogen atom is excited, it emits visible radiation. This radiation is predominantly in the:

A)red.
B)blue.
C)green.
D)yellow.

Question 76

The temperature of hydrogen gas is such that electrons are excited by atomic collisions up to the n = 3 atomic energy levels. Emission lines from which spectral sequences result when electrons return to the ground state?

A)Paschen (IR), Balmer (visible), and Lyman (UV) series
B)Lyman (UV) series only
C)Balmer (visible) and Lyman (UV) series
D)Balmer (visible) series only

Question 77

The strong ultraviolet spectral line emitted by hot hydrogen gas is known as the:

A)21-cm line.
B)Balmer $\alpha$ line.
C)Paschen $\alpha$ line.
D)Lyman $\alpha$ line.

Question 78

The wavelengths λ of the emission lines from hot hydrogen gas depend on an integer n according to:

A)n.
B)1/n².
C)1/n.
D)n².

Question 79

If the wavelengths of H_α and H_ß, the first two lines of the hydrogen Balmer series, are 656.3 nm and 486.2 nm, respectively, what is the wavelength of H_γ, the third line of the Balmer series?

A)486.2 nm
B)1875 nm
C)364.6 nm
D)434.1 nm

Question 80

What type of radiation is emitted by hot hydrogen gas when electrons jump from the n = 8 level to the n = 7 level of the atoms?

A)52,489 m, in the radio
B)1.905 μm, in the near infrared
C)19.05 μm, in the infrared
D)38.9 nm, in the ultraviolet