Exam 5: Light: the Cosmic Messenger

One of the absorption lines of hydrogen has a rest wavelength of 656 nm (at rest means with respect to the observer, like in a lab). You observe several stars and measure the wavelength of this same hydrogen absorption line in each star. Based on the measured wavelength of this line, which star is moving towards the Earth the fastest?

Which of the following objects would be most likely to produce an emission-line spectrum?

The resolution of a 10-meter telescope is about 0.01 arcsecond for visible light. Would you expect the angular resolution of a 10-meter radio telescope to be better than, equal to, or worse than 0.01 arcsecond? Explain.

Betelgeuse is the bright red star representing the left shoulder of the constellation Orion. All the following statements about Betelgeuse are true. Which one can you infer from its red color?

Which of the following statements about electrical charge is true?

Which forms of light are lower in energy and frequency than the light that our eyes can see?

A gas heated to millions of degrees would emit

How can an electron in an atom lose energy to go from a higher energy level to a lower energy level?

X-rays, because they have more energy, travel through space faster than visible light.

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

Briefly explain how we can use spectral lines to determine an object's radial motion (toward or away from us). Can we also learn the object's tangential motion (across our line of sight) from its spectral lines?

An atom that has fewer electrons than protons is called a/an ________.

Which of the following properties of a star can be measured directly, during a single night at the telescope?

The atomic nuclei of the same element always have the same number of neutrons.

We are measuring the spectra of two hydrogen gas clouds. The laboratory frame wavelength of one hydrogen line is 656.2 nm. Cloud A's emission line wavelength is 660.1 nm and Cloud B's emission line wavelength is 670.1 nm. What can we conclude about these clouds?

X-ray telescope mirrors are very similar to optical telescope mirrors.

The greater the wavelength of light, the greater its energy.

Laboratory 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?

The atomic nuclei of the same element always have the same number of protons.

Consider an atom of gold in which the nucleus contains 79 protons and 118 neutrons. What is its atomic number and atomic mass number?