Q&A Hero

Q: A watch dial that continues to glow after a week in the dark is almost certainly A) fluorescent. B) phosphorescent. C) polarized. D) radioactive.

Q: Some light switches that glow in the dark after the lights are turned off employ A) fluorescence. B) resonance. C) incandescence. D) all of the above E) none of the above

Q: Atoms can be excited by A) thermal agitation. B) electron impact. C) photon impact. D) all of the above E) none of the above

Q: Which light-emitting process is characterized by an afterglow? A) incandescence. B) fluorescence. C) phosphorescence. D) resonance. E) none of the above

Q: The major difference between phosphorescent and fluorescent materials is A) a time delay between excitation and de-excitation. B) a difference in brightness. C) the greenish color of phosphorescence. D) none of the above

Q: 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) would violate the law of energy conservation. D) all of the above E) none of the above

Q: A paint pigment that absorbs blue light and gives off red light A) is fluorescent. B) is phosphorescent. C) can be both of these D) neither of these

Q: 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.

Q: Some minerals glow when illuminated with ultraviolet light because A) ultraviolet photons boost atomic electrons in the mineral to higher energy states. B) ultraviolet photons have high energy. C) of selective reflection. D) of selective transmission. E) none of the above

Q: In the process of fluorescence, part of the input energy immediately A) becomes internal energy with the rest as lower-frequency light. B) cascades to excite other atoms in the material. C) is emitted as higher-frequency light and the rest as lower-frequency light. D) excites electrons to metastable states. E) none of the above

Q: 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. D) none of the above

Q: The greater proportion of energy immediately converted to heat rather than light occurs in A) a fluorescent lamp. B) an incandescent lamp. C) both of these D) neither of these

Q: 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.

Q: Fluorescent minerals on display in museums are illuminated with A) infrared light. B) ultraviolet light. C) often either or both D) none of these

Q: Astronomers can detect the spin rates of stars by A) their temperature. B) changes in temperature. C) absorption spectra. D) the Doppler effect. E) all of the above

Q: Astronomers can tell whether a light source approaches or recedes from Earth by A) its temperature. B) its change in temperature. C) its absorption spectra. D) the Doppler effect. E) all of the above

Q: For absorption spectra to exist A) the light source must be a gas. B) partially absorbent material must exist between the light source and the spectroscope slit. C) the spectroscope must be equipped with an absorption cell. D) all of the above E) none of the above

Q: An atom that emits light of a certain frequency is A) not likely to absorb that same frequency. B) an absorber of light of the same frequency. C) fluorescent. D) none of the above

Q: Iron absorption lines that occur in the solar spectrum indicate that iron exists in the solar A) atmosphere. B) surface. C) interior. D) none of the above

Q: Fraunhofer lines are apparent in A) absorption spectra. B) emission spectra. C) Doppler shifts. D) a variety of energy levels. E) none of the above

Q: The dark lines in the Sun's spectrum are due to light that is A) absorbed by the Sun's atmosphere. B) emitted by the Sun. C) reflected by the Sun. D) none of the above

Q: Helium was first discovered in the A) laboratory. B) upper atmosphere. C) Sun. D) island of Helios, in Greece. E) byproducts of nuclear fusion.

Q: If a 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.

Q: If the radiation curve for an incandescent lamp filament peaks in the green region, the object would appear A) red. B) yellow. C) green. D) blue. E) white.

Q: The hottest star is the one that glows A) red. B) white. C) blue. D) need more information

Q: The radiation curve for a blue hot star peaks in the A) infrared region. B) red region. C) yellow region. D) ultraviolet region. E) none of the above

Q: Light at the peak frequency of 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.

Q: The radiation curve for a red hot fire-place poker peaks in the A) infrared region. B) green region. C) ultraviolet region.

Q: A violet-hot star emits radiation having about twice the peak frequency of radiation from a red-hot star. The surface temperature of the hotter star is about A) half that of the cooler star. B) twice that of the cooler star. C) the same.

Q: An object heated to twice the absolute temperature emits radiation A) with twice the peak frequency. B) in the ultraviolet part of the spectrum. C) in the radio wave part of the spectrum. D) with longer wavelengths.

Q: If wavelengths of emitted light become longer, the energy per photon of light A) increases. B) remains constant. C) decreases. D) none of the above

Q: If a certain object emits visible waves rather than infrared waves its temperature is A) higher. B) lower. C) the same, temperature doesn't make any difference.

Q: Sometimes a flashlight filament glows red instead of white, which indicates a lowness of A) current in the filament. B) filament temperature. C) both of these D) neither of these

Q: Which of the following continually emits electromagnetic radiation? A) insects B) radio antennas C) red-hot coals D) all of the above E) none of the above

Q: As the filament of a lamp is heated it changes A) temperature. B) color. C) both of these D) neither of these

Q: Isolated bells ring clearly, while bells crammed in a box have a muffled ring. This is analogous to light emitted by A) a laser. B) a fluorescent lamp. C) an incandescent lamp. D) a phosphorescent source. E) none of the above

Q: As a solid is gradually heated, it first glows A) red. B) yellow. C) white. D) blue.

Q: The spectrum of a mercury vapor lamp under very high pressure appears as that from A) an incandescent source. B) a laser. C) an ultraviolet source. D) a gas other than mercury. E) a monochromatic source.

Q: The spectral lines are more distinct when viewed in a mercury vapor lamp under A) high pressure. B) low pressure. C) same for each

Q: The Doppler effect due to motion of excited atoms in a glowing gas tends to make the spectral lines slightly A) thicker. B) thinner. C) more numerous. D) none of the above

Q: Comparing the light from a glowing tube of neon gas and the beam of a helium-neon laser, there is a greater number of spectral lines in light from the A) neon gas tube. B) laser beam. C) both about the same

Q: Discrete spectral lines are observed when excitation occurs in a A) solid. B) liquid. C) gas. D) superconductor. E) all of the above

Q: If light in a spectroscope were passed through a star-shaped opening instead of a thin slit, spectral lines would appear as A) lines of poorer resolution. B) stars. C) blobs of no definite shape.

Q: If light in a spectroscope passed through round holes instead of slits, spectral lines would appear A) as thicker lines. B) round. C) dimmer.

Q: Spectral lines take the shape of vertical lines because A) the light is vertically polarized. B) they are images of a vertical slit. C) the energy levels in the atom are parallel to one another. D) all of the above E) none of the above

Q: If the energy levels in the neon atom were not discrete, neon signs would glow A) red. B) white. C) blue.

Q: When we say energy levels in an atom are discrete, we mean that their energy levels are well defined and A) separate from one another. B) separated by equal energy increments. C) continuous. D) private.

Q: Green light emitted by excited mercury vapor corresponds to an energy transition in the mercury atom. A more energetic transition might emit A) red light. B) blue light. C) white light. D) any of these

Q: The air that you breathe doesn't emit 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.

Q: Colors seen in the flames of a burning log originate with the variety of A) multi-layered incandescent surfaces. B) electron transitions in various atoms. C) temperatures. D) absorbing gases between the log and the viewer.

Q: Neon atoms in a glass tube can be excited A) once per atom. B) repeatedly. C) by infrared light.

Q: The energy of a photon is related to A) the energy given to the atom that emits it. B) the energy transition in de-excitation. C) its frequency. D) all of the above E) none of the above

Q: An atom that absorbs a certain amount of energy can then emit A) only a photon of that energy. B) a photon of any energy. C) a photon of the same or higher energy. D) a photon of the same or lower energy.

Q: Electrons with greater potential energies relative to the atomic nucleus are A) inner electrons. B) outer electrons. C) both the same

Q: Light is emitted when an electron A) is boosted to a higher energy level. B) makes a transition to a lower energy level. C) accelerates to a medium energy level. D) none of the above

Q: An excited atom is an atom A) with excess vibration. B) with one or more displaced electrons. C) with more protons than electrons. D) that is frantic.

Q: An atom is excited when one or more of its electrons A) vibrates. B) is boosted into higher energy levels. C) undergoes a frequency change. D) becomes frantic.

Q: The best visible safety light in the darkroom that will emit low-energy photons is A) violet. B) blue. C) green. D) any of the above E) none of the above

Q: 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.

Q: The energy per photon in ultraviolet light is greater than in A) radio waves. B) microwaves. C) visible light. D) all of the above E) none of the above

Q: Which color of visible light carries the most energy per photon? A) red B) green C) blue D) violet E) all the same

Q: The highest frequency of visible light is A) red. B) green. C) blue. D) violet. E) all the same

Q: The energy of a photon depends on its A) speed. B) frequency. C) amplitude. D) all of the above E) none of the above

Q: A radio wave and a visible light wave differ only in A) frequency. B) energy per photon. C) both of these D) none of these

Q: A throbbing pulse of electromagnetic radiation is called a A) proton. B) photon. C) phototron. D) newtron. E) nooytron.

Q: Physicists find that the energy states of atoms are A) discrete. B) circular. C) elliptical. D) chaotic.

Q: Magnification can be accomplished with a hologram when viewed with light that has a A) longer wavelength than the original light. B) shorter wavelength than the original light. C) neither for holograms cannot be magnified.

Q: A hologram is simply a A) complex diffraction grating. B) thin sheet of non-cubic transparent crystals. C) pair of semi-crossed polarization filters. D) thin photographic film with microscopic images over the entire surface. E) none of the above

Q: Holograms employ the principle of A) diffraction. B) interference. C) both of these D) neither of these

Q: The function of polarizing filters in viewing 3-D slides or movies is to provide each eye A) the ability to see parallax. B) a balanced intensity. C) an independent left or right-eye view. D) a stereoscopic view. E) with light polarized at right angles to each other.

Q: Three-dimensional viewing was popular in the past with slide projectors. If the slides for left and right positions in the stereo projector are duplicates of each other A) depth can be seen. B) no depth can be seen. C) only parallax can be seen.

Q: Because of absorption, a Polaroid will actually transmit 40% of incident unpolarized light. Two such Polaroids with their axes aligned will transmit A) 0%. B) 40%. C) 100%. D) between 0% and 40%. E) between 40% and 100%.

Q: The amount of light from an incandescent lamp that is transmitted through an ideal Polaroid filter is half, and through a classroom Polaroid filter is A) less than half. B) more than half. C) half.

Q: An ideal Polaroid will transmit 50% of incident sunlight. How much light will be transmitted by two ideal Polaroids oriented with their axes parallel to each other? A) 0% B) 50% C) 100% D) between 0% and 50% E) between 50% and 100%

Q: A pair of crossed Polaroids will transmit light A) of sufficiently long wavelengths. B) that itself is polarized. C) if a third Polaroid at about 45 degrees is inserted between the two.

Q: For a pair of Polaroids with axes at 45 degrees to each other A) light will not pass. B) light that passes is dimmer than for a parallel orientation. C) another Polaroid is necessary for any light to pass.

Q: Light will pass through a pair of Polaroids when their axes are A) 45 degrees to each other. B) parallel. C) either of these D) neither of these

Q: Light will NOT pass through a pair of Polaroids when their axes are A) 45 degrees to each other. B) parallel. C) perpendicular. D) all of the above E) none of the above

Q: A painting looks less flat when viewed with A) one eye. B) both eyes. C) Polaroid glasses.

Q: The polarization axes of glasses for 3-D viewing are A) vertical. B) horizontal. C) at right angles to each other.