Astronomy: Chapter 4 Spectroscopy (T/F)

A heated tungsten filament in a lightbulb provides a good example of an emission spectrum. T/F

False. Correct. This will produce a continuous spectrum.

A tube of gas excited by electricity will emit a continuous spectrum. T/F

False. Correct. This will produce an emission spectrum, not a continuous one.

Light can be absorbed at any wavelength by a dilute gas. T/F

False. For further insight, see the discussion of Kirchoff's laws in section 4.1

All cosmic bodies emit perfect blackbody radiation. T/F

False. In fact, no real cosmic object emits perfect blackbody radiation.

Imagine an emission spectrum produced by a container of hydrogen gas. Changing the amount of hydrogen in the container will change the colors of the lines in the spectrum. T/F

False. Refer to section 4.1

The wavelengths of the emission lines produced by an element are different from the wavelengths of the absorption lines produced by the same element. T/F

False. Refer to section 4.3

An electron can have any energy within an atom, so long as it is above the ground-state energy. T/F

False. Refer to section 4.5

Spectral lines of hydrogen are relatively weak in the Sun because the Sun contains relatively little hydrogen. T/F

False. Refer to section 4.6

Fraunhofer lines are emission lines in the solar spectrum. T.F

False. Refer to section 4.7

The number of electrons in an atom determines the element that it represents. T/F

False. Right. The number of protons, not electrons, determines the identity of an element.

The solar spectrum, like that from any star, contains only emission lines. T/F

False. The dark lines in such spectra are caused by absorption due to the presence of cooler intervening gases in the outer layers of the Sun and other stars.

Each spectral line corresponds to a different element. T/F

False. Yes. A given element produces several lines. Each element does produce a unique set of lines.

Scientists today view atoms as made up of a positively charged nucleus with negatively charged electrons orbiting the nucleus in precisely defined orbits. T/F

False. Yes. Electrons are located around the positively charged nucleus, but not in precisely defined orbits. They are smeared out in the electron cloud. The energy of the electron is precisely defined, however.

Infrared radiation is more dangerous to living cells than ultraviolet radiation because photons of infrared radiation have longer wavelengths than photons of ultraviolet radiation. T/F

False. Yes. Since infrared photons have longer wavelengths than ultraviolet photons, they carry less energy and are less damaging to cells. It is the ultraviolet radiation from the Sun that causes sunburn and skin cancer.

A Photon of blue light has more energy than a photon of green light. T/F

True. Since blue photons have shorter wavelengths (and therefore higher frequencies) than green photons, they are also more energetic.

Electrons can be dislodged from the atoms in a metal by simply shining light on it. T/F

True. The dependence of this "photoelectric effect" on the color, rather than just the intensity, of the light gives further evidence that light is composed of photons.

The photon resulting from a transition between the 1000th and 999th energy levels of an atom would be lower in frequency than one resulting from a transition between the 100th and 99th energy levels of the same atom. T/F

True. The energy difference between the starting and ending levels of an electron transition is equal to the energy of the photon involved in this transition.

A nebula that appears to be an emission nebula to an observer on Earth might appear to be an absorption nebula to an observer in a different location in the galaxy. T/F

True. Yes. Absorption and emission are related by the same atomic processes. Whether a nebula appears as an emission nebula or an absorption nebula depends on the vantage point of the observer.

In the photoelectric effect, the speed with which the particles are ejected from the metal depends only on the color, and not on the intensity of the light. T/F

True. Yes. As discussed in Discovery 4-1, this was one of the key pieces of the puzzle that Einstein had to explain.

The energy levels occupied in an atom may be different at high temperatures than at low temperatures. T/F

True. Yes. At high temperatures the electrons may be found in higher energy levels.

A change in the rotational state of a molecule will in general produce a lower-energy photon than a change in its vibrational state. T/F

True. Yes. Vibrational energy transitions are in general larger than changes in rotational energy, but smaller than transitions between orbital energy states.

Compared with cooler stars, the hottest stars have absorption lines that are A) broad and fuzzy B) thin and distinct C) identical to the lines in the cooler stars

broad and fuzzy Refer to section 4.18

Compared with slowly rotating stars, the fastest spinning stars have absorption lines that are... A) thin and distinct B) broad and fuzzy C) identical to the lines in the slowly rotating stars

broad and fuzzy Refer to section 4.19

Compared with a complex atom line neon, a simple atom such as hydrogen has... A) more excited states B) fewer excited states C) the same number of excited states

fewer excited states Refer to section 4.17

An atom that has been ionized... A) has more protons than electrons B) is electrically neutral C) is radioactive D) has equal numbers of protons and electrons.

has more protons than electrons Refer to section 4.15

Compared with an electron transition from the first excited state to the ground state, a transition from the third excited state to the second excited state emits a photon of.... A) greater energy B) lower energy C) identical energy

lower energy Refer to section 4.16

Rotation of a star can broaden the width (on an intensity versus frequency plot) of its spectral lines. T/F

True Since most stars are distant enough to appear as points even under very high magnification, light rays from all parts of the star merge together to produce wider lines when it is rotating rapidly.

A magnetic field in a star would broaden its spectral lines, but not produce a net Doppler shift. T/F

True. Correct. A magnetic field would only tend to broaden spectral lines, not shift their overall positions within a spectrum.

Line intensity in an atomic emission spectrum depends on the temperature of the atoms. T/F

True. If the gas were very cold, comparatively few atoms would have enough energy to emit photons.

Molecules of a low-density material can rotate and vibrate only at certain specific frequencies. T/F

True. Molecular lines are generally more numerous and complex than the characteristic absorption or emission lines from the individual atoms that make up the molecule.

High temperatures, rotation, and magnetic fields all tend to broaden spectral lines. T/F

True. Refer to section 4.10

Imagine an emission spectrum produced by a container of hydrogen gas. Changing the gas in the container from hydrogen to helium will change the colors of the lines occurring in the spectrum. T/F

True. Refer to section 4.2

The energy of a photon is inversely proportional to the wavelength of the radiation. T/F

True. Refer to section 4.4

Light behaves both as a wave and as a particle. T/F

True. Refer to section 4.8

An electron moves to a higher energy level in an atom after absorbing a photon of a specific energy.

True. Refer to section 4.9

Compared with a spectrum from a ground-based observation, the spectrum of a star-observed from above Earth's atmosphere show... A) no absorption lines B) fewer emission lines C) slightly fewer absorption lines D) many more absorption lines

slightly fewer absorption lines Refer to section 4.11

The visible spectrum of sunlight reflected from Saturn's cold moon Titan would be expected to be... A) continuous B) emission spectrum C) absorption spectrum

absorption spectrum Refer to section 4.12

Compared with a star having many blue absorption lines, a star with many red and blue absorption lines must be... A) cooler than the other star B) moving away from the other star C) moving away from the observer D) of different composition than that of the other star

of different composition than that of the other star Refer to section 4.14