RANDY L. PHELPS

This is the module for "Light and Atoms"

For this module, please look through the "lecture" notes for "Light and Atoms".  These notes contain the material, in condensed form, that I will expect you to become familiar with.  I am sure you will have questions about the material, especially since it is presented in the form of lecture notes.  To help you expand upon the material, and fill in some blanks, check out the following web sites:

Upon completion of this web assignment, you should be comfortable with the following material:

• The types of electromagnetic radiation, their relative order in terms of wavelength, frequency and energy, and whether they can be observed from the Earth's surface, the upper atmosphere, or only from space.
• Kirchoff's Laws and how they can be applied to learn about astrophysical objects.
• How the Bohr atom explains Kirchoff's 2nd and 3rd laws.
• How temperature can be determined from Wien's Law.
• The Doppler effect, what causes it, and what one can learn from it.
• How various types of electromagnetic energy originate (e.g., infrared and radio).

Upon completion of this assignment, you should be able to answer these, and similar, questions

• What three quantities describe a wave?
• Which form of electromagnetic energy has the longest wavelength, radio waves or visible light?
• Which form of electromagnetic energy has the longest wavelength, infrared light or visible light?
• Which form of electromagnetic energy has the shortest wavelength, xrays or radio waves?
• Which form of electromagnetic energy has the highest frequency, radio waves or visible light?
• Which form of electromagnetic energy has the highest frequency, xrays or ultraviolet light?
• Which form of electromagnetic energy has the lowest frequency, radio waves or gamma-rays?
• Which form of electromagnetic energy has the highest energy, x-rays or gamma-rays?
• Which form of electromagnetic energy has the highest energy, x-rays or visible light?
• Which form of electromagnetic energy can be detected from Earth's surface, radio waves or gamma-rays?
• Which form of electromagnetic energy must be detected from space, visible light or gamma-rays?
• Which form of electromagnetic energy can be detected from Earth's upper atmosphere, some infrared or x-rays?
• What are Kirchoff's Laws, and what does each one describe?
• If one sees a continuous spectrum, what description of the physical characteristics of the emitting object can be made?
• If one sees an emission spectrum, what description of the physical characteristics of the emitting object can be made?
• If one sees an absorption spectrum, what description of the physical characteristics of the emitting object can be made?
• If one sees an emission spectrum with red, blue and purple lines, what description of the physical characteristics of the emitting object can be made?
• If one sees an absorption spectrum, with red, blue and purple lines missing, what description of the physical characteristics of the emitting object can be made?
• "Quantization" means what, in terms of the orbits of an electron in an atom?
• To go from a lower orbit to a higher orbit in an atom, how must the energy of an electron change?
• If an electron goes from a higher orbit in an atom, and then returns to the same orbit from which it started, what can be said about the changes in the electron energy?
• What is the observable consequence when electrons gain/lose energy in terms of photons?
• The visible light spectrum of Hydrogen occurs when electrons start/end up from which orbits, or energy levels?
• If two solid objects are heated to high temperatures, but one is still hotter than the other, how will their colors differ?
• If two dense, gaseous objects are heated to high temperatures, but one is still hotter than the other, how will their colors differ?
• If the temperature of an object increases, how does the wavelength at which the maximum light is emitted change?
• What is the Kelvin temperature scale?
• The Doppler effect measures changes in what component of the total velocity of an object?
• If an object is receding from you, how will the observed spectral lines in a star change?
• If an object is approaching you, how will the observed spectral lines in a star change?
• If two objects are receding from you, and one is traveling faster than the other, how will the spectral line shifts differ?
• When an electron changes "spin", what wavelength does the emitted electromagnetic energy have?  In what part of the electromagnetic spectrum does this correspond to?
• When molecules change vibration states, what type of electromagnetic radiation is emitted?
• When molecules change rotation states, what type of electromagnetic radiation is emitted?

• If you take a spectrum of a star, which of the three types of spectra described by Kirchoff would you see?
• An engineer designing a new filament light bulb would expect to see which of the three types of spectra described by Kirchoff?
• The Orion Nebula is a thin gas in space that is being heated by nearby hot stars. If you take a spectrum of the Orion Nebula, which of the three types of spectra described by Kirchoff would you see?
• The Ring Nebula is a thin gas in space that is being heated by a hot star that once was like the Sun, but which has "died" and become a white dwarf. If you take a spectrum of the Ring Nebula, which of the three types of spectra described by Kirchoff would you see?
• Tiny solid dust grains are located in regions where stars form. They are heated from radiation from newly forming stars and from the so-called Cosmic Background Radiation. If you take a spectrum of the dust grains, which of the three types of spectra described by Kirchoff would you see?
• Galaxies are collections of hundreds of millions, to hundreds of billions of stars.   If you take a spectrum of a galaxy, which of the three types of spectra described by Kirchoff would you see?
• Two stars are observed to have Calcium spectral lines shifted toward longer wavelengths. Star 1 has spectral lines shifted by 20 Angstroms, while star 2 has spectral lines shifted by 35 Angstroms.  What can be said about these two stars?
• Stars form in cold, dusty clouds of gas called molecular clouds.  In what part of the electromagnetic spectrum should one study how stars form?
• The presence of a black hole can often be inferred by detecting gas colliding at high velocites in a disk around the black hole.  In what part of the electromagnetic spectrum should one study black holes?

These questions, and similar ones, will form the basis of  the exam material for this section of the course.  If you have problems with the material, please see me during my office hours. If you are unable to answer some of the questions, I will help you before the date specified on the syllabus, provided you show me the results of your inquiry into the material.

That is, you must provide me the answers you we able to obtain for all questions, including your attempts at problem questions, before I will help you with any of them!   

In other words, for me to provide you with help with the questions, you must show me that you have undertaken a good-faith-effort to find the answers yourself, in a timely manner.