Florida National University Multiple Choice Exam Practice

4 PointsThe energy levels for electrons vary from one element to another.

1. True
2. False

4 PointsAccording to the laws of thermal radiation, hotter objects emit photons with ________.

1. a lower average frequency
2. a higher average speed
3. a lower average energy
4. a shorter average wavelength

4 PointsWhen an electron in an atom goes from a higher energy state to a lower energy state, the atom

1. absorbs several photons of a specific frequency.
2. emits a photon of a specific frequency.
3. can emit a photon of any frequency.
4. absorbs a photon of a specific frequency.
5. can absorb a photon of any frequency.

4 PointsThe spectra of most galaxies show redshifts. This means that their spectral lines ________.(See Doppler Effect shift.)

1. have a higher intensity in the red part of the spectrum
2. have wavelengths that are shorter than normal
3. have wavelengths that are longer than normal
4. always are in the red part of the visible spectrum

4 PointsThermal radiation is defined as ________.

1. radiation that is felt as heat radiation in the form of emission lines from an object
2. radiation produced by an extremely hot object
3. radiation with a spectrum whose shape depends only on the temperature of the emitting object

4 PointsIf you heat a gas so that collisions are continually bumping electrons to higher energy levels, when the electrons fall back to lower energy levels the gas produces

1. radio waves.
2. an absorption line spectrum.
3. thermal radiation.
4. an emission line spectrum.
5. X-rays.

4 PointsSuppose you look at a spectrum of visible light by looking through a prism or diffraction grating. How can you decide whether it is an emission line spectrum or an absorption line spectrum?

1. An emission line spectrum consists of a long bright line, while an absorption line spectrum consists of a long dark line.
2. An emission line spectrum consists of bright lines on a dark background, while an absorption line spectrum consists of dark lines on a rainbow background.
3. The emission line spectrum is produced by electrons jumping up in energy level, while the absorption line spectrum is produced by electrons jumping down in energy level.
4. The only way to decide is to make a graph of the intensity of the light at every wavelength, and then analyze the graph carefully.

4 PointsWhich of the following observational techniques is most appropriate for measuring Doppler shifts?

1. timing (measuring how the amount of light changes with time)
2. spectroscopy (taking a spectrum)
3. imaging (taking a picture)

4 PointsOne star is emitting primarily visible light and another star is emitting primarily infrared light. Which star is hotter?

1. The temperature also depends on the radius of the star, so one can’t decide based on the information provided.
2. the star emitting visible light
3. Both stars are the same temperature.
4. the star emitting infrared light

4 PointsLines of a particular element appear at the same wavelength in both emission and absorption line spectra.

1. True
2. False

4 PointsLaboratory measurements show hydrogen produces a spectral line at a wavelength of 486.1 nanometers (nm). A particular star’s spectrum shows the same hydrogen line at a wavelength of 486.0 nm. What can we conclude?

1. The star is moving away from us.
2. The star is moving toward us.
3. The star is getting colder.
4. The star is getting hotter.

4 PointsSuppose you see two stars: a blue star and a red star. Which of the following can you conclude about the two stars? Assume that no Doppler shifts are involved. (Hint: Think about the laws of thermal radiation.)

1. The blue star is more massive than the red star.
2. The red star has a hotter surface temperature than the blue star.
3. The red star is more massive than the blue star.
4. The blue star is farther away than the red star.
5. The blue star has a hotter surface temperature than the red star.

4 PointsSuppose you want to know the chemical composition of a distant star. Which piece of information is most useful to you?

1. the Doppler shift of the star’s spectrum
2. the wavelengths of spectral lines in the star’s spectrum
3. whether the star’s spectrum has more emission lines or more absorption lines
4. the peak energy of the star’s thermal radiation

4 PointsWhat is the angular resolution of the human eye?

1. about 1 milliarcsecond
2. about 1 arcsecond (1/3600 of a degree)
3. about 1 degree
4. about 1 arcminute, or 1/60 of a degree

4 PointsX-rays from astronomical objects can only be detected from telescopes in space.

1. True
2. False

4 PointsWhat do astronomers mean by light pollution?

1. Light pollution is light from human sources that makes it difficult to see the stars at night.
2. Light pollution is a type of air pollution created by lightweight gases such as hydrogen and helium.
3. Light pollution means contamination of light caused by chemicals in the Earth’s atmosphere.
4. Light pollution is a term used to describe the appearance of the sky in regions that are crowded with stars.

4 PointsWhich of the following statements best describes the two principle advantages of telescopes over eyes?

1. Telescopes can collect far more light with far greater magnification.
2. Telescopes collect more light and are unaffected by twinkling.
3. Telescopes have much more magnification and better angular resolution.
4. Telescopes can collect far more light with far better angular resolution.

4 PointsA typical atom has a size of about

1. 1 nanometer (10-9 meters).
2. 1 picometer (10-12 meters).
3. 1 millimeter (10-3 meters).
4. 1 Angstrom (10-10 meters).

4 PointsIf a material is transparent, then it

1. transmits light well.
2. absorbs light well.
3. reflects light well.
4. scatters light well.
5. emits light well.

4 PointsWe can see each other in the classroom right now because we

1. reflect infrared light.
2. emit visible light.
3. emit infrared light.
4. emit thermal radiation.
5. reflect visible light.

4 PointsWhen considering light as made up of individual “pieces,” each characterized by a particular amount of energy, the pieces are called ________.

1. wavicles
2. photons
3. gamma rays
4. frequencies

4 PointsThe atomic nuclei of the same element always have the same number of protons.

1. True
2. False

4 PointsWhich of the following statements about electrical charge is true?

1. Two negative charges will attract each other.
2. Two positive charges will attract each other.
3. A positive charge and a negative charge will attract each other.
4. A positive charge and a negative charge will repel each other.

4 PointsThe wavelength of a wave is

1. how strong the wave is.
2. the distance between where the wave is emitted and where it is absorbed.
3. the distance between a peak of the wave and the next trough.
4. the distance between two adjacent peaks of the wave.
5. equal to the speed of the wave times the wave’s frequency.

4 PointsThe greater the wavelength of light, the greater its energy.

1. True
2. False