5 Written Questions
5 Matching Questions
- If a material is highly opaque, then it
A) reflects most light.
B) absorbs most light.
C) transmits most light.
D) scatters most light.
E) emits most light.
- Electrons orbit an atomic nucleus like planets orbit the Sun.
- Visible light from a distant star can be spread into a spectrum by using a glass prism or ________.
A) a diffraction grating
B) adaptive optics
C) a telescope
D) a flat glass mirror
- Which of the following transitions within an atom is not possible?
A) An electron begins in an excited state and then gains enough energy to jump to the ground state.
B) An electron begins in the ground state and then gains enough energy to jump to an excited state.
C) An electron begins in the ground state and then gains enough energy to become ionized.
D) An electron begins in an excited state and then gains enough energy to become ionized.
- Suppose the surface temperature of the Sun were about 18,000 K, rather than 6,000 K. How much more thermal radiation would the Sun emit? How would the thermal radiation spectrum of the Sun be different?
- a False
- b A) a diffraction grating
- c From the first rule of thermal radiation, we know that tripling the temperature of an object increases the amount of thermal radiation it emits per unit area by a factor of 34 = 81. Thus, increasing the surface temperature of the Sun from 6,000 K to 18,000 K would increase its thermal radiation by a factor of 81. The higher temperature of the Sun would shift the peak of its thermal radiation spectrum from its current place in the visible light region into the ultraviolet. The hotter Sun would emit more energy at all wavelengths, with the greatest output coming in the ultraviolet.
- d B) absorbs most light.
- e A) An electron begins in an excited state and then gains enough energy to jump to the ground state.
5 Multiple Choice Questions
- B) The star is moving away from us.
- A) A hot object emits more radiation per unit surface area than a cool object.
- U-238 has 146 neutrons, and U-235 has 3 fewer, or 143 neutro
- A) Power is the rate at which energy is used, so its units are a unit of energy divided by a unit of time.
- A) Electrons orbit the nucleus rather like planets orbiting the Sun.
5 True/False Questions
If 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
A) thermal radiation.
B) an absorption line spectrum.
C) an emission line spectrum.
D) X rays.
E) radio waves. → C) an emission line spectrum.
Which of the following statements about X rays and radio waves is not true?
A) X rays have shorter wavelengths than radio waves.
B) X rays and radio waves are both forms of light, or electromagnetic radiation.
C) X rays have higher frequency than radio waves.
D) X rays have higher energy than radio waves.
E) X rays travel through space faster than radio waves. → A) X rays travel through space faster than radio waves.
An atom in an excited state contains more of what type of energy than the same atom in the ground state?
B) kinetic energy
C) thermal energy
D) gravitational potential energy
E) electric potential energy → D) 81 times more energy.
Suppose you had molecular oxygen (O2) chilled enough so that it was in liquid form. Which of the following best describes the phase changes that would occur as you heated the liquid oxygen to high temperature?
A) It would evaporate into a gas, then the molecules would dissociate into individual oxygen atoms, then the atoms would become increasingly ionized as you continued to raise the temperature.
B) The liquid molecules would quickly dissociate into a liquid of individual oxygen atoms. These atoms would then evaporate into a gas, and then become ionized to make a plasma.
C) It would sublimate into a gas, then the molecules would lose electrons until no electrons were left, then the molecules would dissociate into individual oxygen nuclei.
D) The cold temperature would first cause the oxygen to solidify. The solid would then sublimate into a gas, which would then become a plasma as the molecules lost their electrons, until finally it consisted of bonded pairs of oxygen nuclei stripped bare of any electrons. → A) 6,000 joules
Lines of a particular element appear at the same wavelength in both emission and absorption line spectra → C) its wavelength and energy