Deck 30: Light Emission

Question 1

Fluorescent minerals on display in museums are illuminated with

A)infrared light.
B)ultraviolet light.
C)often either or both
D)none of these

Answer 1

ultraviolet light.

Question 2

Light from two closely spaced stars will not produce a steady interference pattern at the Earth's surface because of

A)incoherence.
B)the inherent instability of the atmosphere.
C)their different radial distances.
D)their non-point like natures.
E)Closely spaced stars do produce interference patterns.

Answer 2

incoherence.

Question 3

Electrons with the greater potential energies with respect to the atomic nucleus are

A)inner electrons.
B)outer electrons.
C)both the same,actually

Answer 3

outer electrons.

Question 4

A photographer wishes to use a safety light in the darkroom that will emit low-energy photons.The best visible color to use is

A)violet.
B)blue.
C)green.
D)actually any of these
E)none of these

Question 5

An excited atom is an atom

A)that has excess vibration.
B)that has one or more displaced electrons.
C)with more protons than electrons.
D)that is frantic.

Question 6

To say that energy levels in an atom are discrete is to say the energy levels are well defined and

A)separate from one another.
B)separated from one another by the same energy increments.
C)continuous.
D)private.

Question 7

Discrete spectral lines occur when excitation takes place in a

A)solid.
B)liquid.
C)gas.
D)superconductor.
E)all of these

Question 8

Which color of light carries the most energy per photon?

A)red
B)green
C)blue
D)violet
E)all the same

Question 9

Atoms of neon in a glass tube can be excited

A)once per atom.
B)over and over again.

Question 10

The energy of a photon is related to

A)the energy given to the atom that emits it.
B)the energy level difference though which it falls.
C)its frequency.
D)all of these
E)none of these

Question 11

Ultraviolet light is

A)more energetic than X-rays.
B)produced by crossed Polaroids.
C)electromagnetic energy.
D)present everywhere.
E)none of these

Question 12

The greater proportion of energy immediately converted to heat rather than light occurs in

A)a fluorescent lamp.
B)an incandescent lamp.
C)both the same

Question 13

Compared to the energy of a photon of red light,the energy of a photon of blue light is

A)less.
B)more.
C)the same.

Question 14

The highest frequency light of those below is

A)red.
B)green.
C)blue.
D)violet.
E)all the same

Question 15

Light is emitted when an electron

A)is boosted to a higher energy level.
B)makes a transition to a lower energy level.
C)neither of these

Question 16

The variety of colors seen in a burning log comes from the variety of

A)multi-layered incandescent surfaces.
B)electron transitions in various atoms.
C)temperatures.
D)chemicals in the log.
E)absorbing gases between the log and the viewer.

Question 17

A throbbing pulse of electromagnetic radiation is called a

A)proton.
B)photon.
C)lightron.
D)sparktron.
E)notron.

Question 18

An atom that absorbs a photon of a certain energy can then emit

A)only a photon of that energy.
B)a photon of any energy.
C)only a photon of the same or higher energy.
D)only a photon of the same or lower energy.

Question 19

Light frequency from an incandescent lamp depends on the

A)amount of electrical energy transformed.
B)rate of atomic and molecular vibrations.
C)voltage applied to the lamp.
D)electrical resistance of the lamp.
E)transparency of glass.

Question 20

Light from a lit match comes from

A)electrons.
B)protons.
C)neutrons.
D)all of these

Question 21

Spectral lines take the shape of vertical lines because

A)the light is vertically polarized.
B)they are simply images of a vertical slit.
C)the energy levels in the atom are parallel to one another.
D)all of these
E)none of these

Question 22

Atoms can be excited by

A)thermal agitation.
B)electron impact.
C)photon impact.
D)all of these
E)none of these

Question 23

If the energy levels in the neon atom were not discrete,neon signs would glow

A)red.
B)white.
C)blue.

Question 24

Compared to the energy put into a laser,the energy of the laser beam is

A)more.
B)less.
C)the same.

Question 25

If light in a spectroscope passed through round holes instead of slits,spectral lines would appear

A)as thicker lines.
B)round.
C)dimmer.

Question 26

Helium was first discovered in the

A)laboratory.
B)upper atmosphere.
C)sun.
D)island of Helios,in Greece.
E)by-products of nuclear fusion.

Question 27

In the process of fluorescence,part of the input energy immediately

A)becomes internal energy and the rest lower-frequency light.
B)cascades to excite other atoms in the material.
C)is emitted as higher-frequency light and the rest lower- frequency light.
D)excites electrons to metastable states.
E)none of these

Question 28

The fact that iron absorption lines occur in the solar spectrum directly indicates that there is iron in the solar

A)atmosphere.
B)surface.
C)interior.

Question 29

The main visible difference between phosphorescent and fluorescent materials is

A)an afterglow.
B)a difference in brightness.
C)the greenish color of phosphorescence.

Question 30

The dark lines in the sun's spectrum represent light that is

A)absorbed by the sun's atmosphere.
B)emitted by the sun.
C)not emitted by the sun.

Question 31

Green light emitted by excited mercury vapor corresponds to a particular energy transition in the mercury atom.A more energetic transition might emit

A)red light.
B)blue light.
C)either red or blue light.
D)white light.

Question 32

The fact that the air you breathe doesn't give off much visible light indicates that most of the electrons of its atoms are

A)in the ground state.
B)excited to metastable states.
C)relatively cool.
D)electrically neutral.
E)relatively far apart.

Question 33

An atom that emits a certain frequency of light is

A)not likely to absorb that same frequency.
B)an absorber of the same frequency.

Question 34

Light from a laser is

A)monochromatic.
B)in phase.
C)coherent.
D)all of these
E)none of these

Question 35

Astronomers can tell whether a star is approaching or receding from Earth by

A)its temperature.
B)its change in temperature.
C)its absorption spectra.
D)the Doppler effect.
E)all of these

Question 36

The efficiency of classroom lasers is typically

A)about one percent.
B)about ten percent.
C)about twenty percent.
D)appreciably more than twenty percent.

Question 37

If light in a spectroscope were passed through a star-shaped opening instead of a thin slit,spectral lines would appear as

A)lines,but with poorer resolution.
B)stars.
C)blobs of no definite shape.

Question 38

In the process of fluorescence,the input is high-frequency light and the output is

A)higher-frequency light.
B)equally high-frequency light.
C)lower-frequency light.

Question 39

Isolated bells ring clear,while bells crammed in a box have a muffled ring.If the sound of isolated bells is analogous to light from a gas discharge tube,then sound from the box crammed with bells is analogous to light from

A)a laser.
B)a fluorescent lamp.
C)an incandescent lamp.
D)a phosphorescent source.
E)none of these

Question 40

The white light emitted by a fluorescent lamp is provided by the

A)mercury vapor in the lamp.
B)phosphors on the inner surface of the lamp.
C)high temperature of the glowing gas.
D)filtering effect of the glass tubing.

Question 41

A certain object emits infrared waves.If it were to emit light waves instead,its temperature would have to be

A)higher.
B)lower.
C)the same,temperature doesn't make any difference.

Question 42

The hottest star is the star that glows

A)red.
B)white.
C)blue.
D)cannot be determined by color alone

Question 43

The spectral lines are more distinct when viewed in a mercury vapor lamp under

A)high pressure.
B)low pressure.
C)same for each

Question 44

Light from a phosphorescent source

A)takes longer to travel from the source to you.
B)normally has a shorter wavelength than the light that initially produced it.
C)is cooler than light from a fluorescent source.
D)all of these
E)none of these

Question 45

A paint pigment that absorbs red light and gives off blue light

A)is fluorescent.
B)is phosphorescent.
C)is used in lasers.
D)is polarized.
E)doesn't exist.

Question 46

The Doppler effect from the back-and-forth motion of atoms in a glowing discharge tube tends to make the spectral lines slightly

A)thicker.
B)thinner.
C)more numerous.
D)none of these

Question 47

A paint pigment that absorbs blue light and gives off red light

A)is fluorescent.
B)is phosphorescent.
C)is used in lasers.
D)is fluorescent or phosphorescent.
E)doesn't exist.

Question 48

The absorption of an infrared photon that excites an atom to emit a green photon

A)occurs in plants.
B)occurs in the process of phosphorescence.
C)violates the law of energy conservation.
D)all of these
E)none of these

Question 49

Some light switches glow in the dark after the lights are turned off.This is because of

A)fluorescence.
B)resonance.
C)incandescence.
D)a time delay between excitation and de-excitation.
E)none of these

Question 50

For absorption spectra to exist

A)the light source must be a gas.
B)partially absorbent material must exist between the light source and spectroscope.
C)the spectroscope must be equipped with an absorption cell.
D)all of these
E)none of these

Question 51

Which of the following continually emits electromagnetic radiation?

A)insects
B)radio antennas
C)red-hot coals
D)all of these
E)none of these

Question 52

Comparing the light from a glowing tube of neon gas with light in the beam of a helium-neon laser,we find the greater number of spectral lines in light from the

A)neon gas tube.
B)laser beam.
C)both about the same

Question 53

The radiation curve for a "red hot" object peaks in the

A)infrared region.
B)green region.
C)ultraviolet region.

Question 54

The energy of a photon depends on its

A)speed.
B)frequency.
C)amplitude.
D)all of these
E)none of these

Question 55

A watch dial that continues to glow after a week in the dark is almost certainly

A)fluorescent.
B)phosphorescent.
C)polarized.
D)radioactive.

Question 56

The radiation curve for a "blue hot" object peaks in the

A)infrared region.
B)red region.
C)yellow region.
D)ultraviolet region.
E)none of these

Question 57

Which light source is more energy-efficient?

A)a fluorescent lamp
B)an incandescent lamp
C)both about the same

Question 58

Some minerals glow when illuminated with ultraviolet light.This is because

A)ultraviolet photons kick atomic electrons in the mineral into higher energy states.
B)ultraviolet photons have such high energy.
C)of selective reflection.
D)of selective transmission.
E)none of these

Question 59

The red laser beam from a helium-neon laser corresponds to a spectral line of

A)helium.
B)neon.
C)both of these
D)neither of these

Question 60

Sometimes a flashlight filament glows red instead of white.This indicates a lowness of

A)current in the filament.
B)battery strength.
C)filament temperature.
D)all of these
E)none of these

Question 61

As a solid is gradually heated,the first color to glow is

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

Question 62

If the radiation curve for an incandescent object peaks in the green region,the object would appear

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

Question 63

Under very high pressure,the spectrum of a mercury vapor lamp begins to look like that from

A)an incandescent source.
B)a laser.
C)an ultraviolet source.
D)a gas other than mercury.
E)a monochromatic source.

Question 64

No laser can emit more energy than is put into it.Can a laser emit more power than is put into it?

A)No.
B)Yes,although not continuously.
C)It is too early in our technological development to answer this question with a reasonable degree of certainty.

Question 65

Materials can be heated until "red hot." If some material is heated until it is "green hot," then

A)it would liquefy immediately.
B)it would be hotter than "white hot."
C)its molecules would be vibrating at nearly identical rates.
D)it would be a strong absorber of red light.
E)energy conservation would be violated.