Question: Thermal radiation is defined as _________.

Answer: radiation with a spectrum whose shape depends only on the temperature of the emitting object

Question: Suppose 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?

Answer: 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.

Question: Which of the following best describes the fundamental difference between two different chemical elements (such as oxygen and carbon)?

Answer: They have different numbers of protons in their nucleus.

Question: Suppose you know the frequency of a photon and the speed of light. What else can you determine about the photon?

Answer: its wavelength and energy

Question: Which of the following statements best describes the two principle advantages of telescopes over eyes?

Answer: Telescopes can collect far more light with far better angular resolution.

Question: Suppose you watch a leaf bobbing up and down as ripples pass it by in a pond. You notice that it does two full up and down bobs each second. Which statement is true of the ripples on the pond?

Answer: They have a frequency of 2 hertz.

Question: If we say that a material is opaque to ultraviolet light, we mean that it _________.

Answer: absorbs ultraviolet light

Question: According to the laws of thermal radiation, hotter objects emit photons with _________.

Answer: a shorter average wavelength

Question: Suppose you want to know the chemical composition of a distant star. Which piece of information is most useful to you?

Answer: the wavelengths of spectral lines in the star’s spectrum

Question: The stars in our sky twinkle in brightness and color because of _________.

Answer: turbulence in Earth’s atmosphere