Exam 5: Light and Matter: Reading Messages from the Cosmos

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

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 perfectly opaque object that absorbs all radiation and reemits the absorbed energy as thermal radiation is

The following questions refer to the diagram below.The levels represent energy levels in a hydrogen atom.Each level is labeled with its energy (above the ground state of Level 1)in units of electron/volts (eV).The labeled transitions represent an electron moving between energy levels. -Which transition represents an electron that is breaking free of the atom?

The study of energy levels in atoms is called

From laboratory measurements,we know that a particular spectral line formed by hydrogen appears at a wavelength of 121.6 nanometers (nm).The spectrum of a particular star shows the same hydrogen line appearing at a wavelength of 121.8 nm.What can we conclude?

If two objects are the same size but one object is 3 times hotter than the other object,the hotter object emits

Which of the following statements about X-rays and radio waves is not true?

Suppose a photon has a frequency of 300 million hertz (300 megahertz).What is its wavelength?

The most common isotope of oxygen has atomic number 8 and atomic weight 16.Another isotope has two extra neutrons.What are the atomic number and atomic weight of this isotope?

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

The most common isotope of gold has atomic number 79 and atomic weight 197.How many protons and neutrons does the gold nucleus contain? Assuming the gold is electrically neutral,how many electrons does it have? If the gold is triply ionized,how many electrons does it have?

Suppose you built a scale-model atom in which the nucleus is the size of a tennis ball.About how far would the cloud of electrons extend?

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

The following questions refer to the diagram below.The levels represent energy levels in a hydrogen atom.Each level is labeled with its energy (above the ground state of Level 1)in units of electron/volts (eV).The labeled transitions represent an electron moving between energy levels. -Which transition represents the electron that emits a photon with the highest energy?

If you have a 100-watt light bulb,how much energy does it use each minute?

Briefly explain why spectral lines are useful in determining the chemical composition of their source.

You observe a distant galaxy.You find that a spectral line normally found in the visible part of the spectrum is shifted toward the infrared.What do you conclude?

Suppose 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. )

The wavelength of a wave is