Questions and Answers of Inquiry into Physics

What is the difference between a continuous spectrum and an emission-line spectrum?
If sunlight can be conceived of as a beam of photons, each of which carries a certain amount of energy and momentum, why don’t we experience (or feel) any recoil as these particles collide with our
Based on what you learned about image formation in Chapter 9, describe how you might design a photocopying machine that could make a copy that is enlarged or reduced compared to the size of the
What aspects of the photoelectric effect can be explained without recourse to the concept of the photon? What aspects of this phenomenon require the existence of photons for their explanation?
Can you think of a reason why metals exhibit the photoelectric effect most easily? (Do you see any connection between this phenomenon and the properties of a good electrical or thermal conductor?)
Sodium undergoes the photoelectric effect, with one electron absorbing a photon of violet light and another absorbing a photon of ultraviolet light. What is different about the two electrons
If Nature suddenly changed and Planck’s constant became a much larger number, what effect would this have on things such as solar cells, atomic emission and absorption spectra, lasers, and so on?
What is a photon? How is its energy related to its frequency? To its wavelength?
What assumption allowed Planck to account for the observed features of blackbody radiation?
Two common controls in a car are the steering wheel and the windshield wiper speed selector. Indicate whether each is controlling something in a quantized or a continuous fashion.
How might you explain the concept of quantization to a younger child (brother, sister, niece, etc.), using money as the quantized entity?
Of the things that a car owner has to purchase routinely—gasoline, oil, antifreeze, tires, spark plugs, and so on—which are normally sold in quantized units, and which are not?
What does it mean when we say that the energy of something is “quantized”?
Section 10.8 introduces the laser as a device whose development followed closely from our understanding of quantum mechanics and atomic structure. Make a list of the basic concepts related to the
Quantum mechanics is one of the most daunting of all areas in physics. To students encountering this subject for the first time at the introductory level, quantum mechanics can seem mysterious, even
A friend tells you that physicists have just invented a new pulsed laser that is pumped with yellow light and produces laser light in the ultraviolet portion of the EM spectrum. Why might you be a
Define what is meant by the term population inversion. Why must this condition be achieved before a system can successfully function as a laser?
Distinguish between a metastable state and a normally allowed energy state within an atom. Discuss the role of metastable states in the operation of laser systems.
Distinguish laser light from the light emitted by an ordinary lightbulb in as many ways as you can.
What is the origin of the word laser?
Describe how the Bohr model may be used to account for characteristic x-ray spectra in heavy atoms.
Will the frequency of the Ka peak in the x-ray spectrum of copper (Cu) be higher or lower than the frequency of the Ka peak of tungsten (W)? Explain how you arrived at your answer.
The x-ray spectrum of a typical heavy element consists of two parts. What are they? How is each produced?
Radioactive strontium (Sr) tends to concentrate in the bones of people who ingest it. Why might one expect that strontium would behave like calcium (Ca) chemically and thus be preferentially bound in
In what part of the EM spectrum does the Lyman series of emission lines from hydrogen lie? The Balmer series? The Paschen series? Describe how each of these series is produced. In what final state do
What would an energy-level diagram look like for the quantized cat in Figure 10.3? (a) (b) istockphoto. com/nico_blue
Will the energy of a photon that ionizes a hydrogen atom from the ground state be larger than, smaller than, or equal to, the energy of a photon that ionizes another hydrogen atom from the first
Explain why a hydrogen atom with its electron in the ground state cannot absorb a photon of just any energy when making a transition to the second excited state (n = 3).
What does it mean when a hydrogen atom is said to be in its “ground state”?
Explain why the Bohr model of the atom is incompatible with the Heisenberg uncertainty principle.
What is the uncertainty principle?
In an electron microscope, electrons play the role that light does in optical microscopes. What makes this possible?
During the normal operation of nuclear power plants and nuclear processing facilities, machinery, building materials, and other things can become radioactive even if they never come into physical
If the binding energy per nucleon (see the graph in Figure 11.16) increased steadily with ass number instead of peaking around A = 56, would nuclear fission and nuclear fusion reactions work
Careful measurements of the mass of a hydrogen-3 nucleus (tritium) yield a value of 3.01605 u. Compute the binding energy in MeV and the binding energy per nucleon for this radioactive nuclide.
Suppose that the mass of the proton and the mass of the neutron were each exactly 1.0 u. What would the mass defect for a copper-63 nucleus be under these circumstances if its atomic mass is 62.5 u?
A nucleus of element 112—copernicium—is formed using the reaction equation given near the end of Section 11.7. It then undergoes six successive alpha decays. Give the identity of the isotope that
The amount of carbon-14 in an ancient wooden bowl is found to be one-half that in a new piece of wood. How old is the bowl?
Iodine-131, a beta emitter, has a half-life of 8 days. A 2-gram sample of initially pure iodine-131 is stored for 32 days. How much iodine-131 remains in the sample afterward?
Iron-58 and bismuth-209 fuse into a large nucleus plus a neutron. Write the reaction equation and determine the identity of the resulting nucleus.
Two deuterium nuclei can undergo two different fusion reactions. One of them is given at the beginning of Section 11.7. In the second possible reaction, two deuterium nuclei fuse to form a new
The following is a possible fission reaction. Determine the identity of the missing nucleus. in + U → U* → Y + ? + 2}n 9BY + ? + 2,n 39
A nucleus of oxygen-15 undergoes electron capture. Write out the reaction equation and determine the identity of the daughter nucleus.
The isotope helium-6 undergoes beta decay. Write the reaction equation and determine the identity of the daughter nucleus.
How can a nucleus of uranium-235 be induced to fission? Describe what happens to the nucleus.
The half-lives of most radioisotopes used in nuclear medicine range between a few hours and a few weeks. Why?
The half-life of plutonium-238, the isotope used to generate electricity on the Voyager spacecraft, is about 88 years. What effect might this have on the spacecraft’s anticipated useful lifetime?
One cause of uncertainty in carbon-14 dating is that the relative abundance of carbon-14 in atmospheric carbon dioxide is not always constant. If it is discovered that during some era in the past
How is carbon-14 used to determine the ages of wood, bones, and other artifacts?
A large number of regular six-sided dice are shaken together in a box, then dumped onto a table. Those showing 1 or 2 are removed, and the process is repeated with the remaining ones. Is the
One-half of the nuclei of a given radioisotope decays during one half-life. Why doesn’t the remaining half decay during the next half-life?
Explain the concept of nuclear half-life.
A concrete wall in a building is found to contain a radioactive isotope that emits alpha radiation. What could be done to protect people from the radiation (short of razing the building)? What if it
A standard treatment for some cancers inside the body is to use nuclear radiation to kill cancer cells. If the radiation has to pass through normal tissue before reaching the cancer, why would alpha
The deflection of an alpha particle as it passes through a magnetic field is much less than the deflection of a beta particle (Figure 11.3). Explain why. Alpha Gamma Beta
A nuclear explosion far out in space releases a large amount of alpha, beta, and gamma radiation. Which of these would be detected first by a radiation detector on Earth?
Describe the common types of radioactive decay. What effect does each have on a nucleus?
What aspects of the composition of a nucleus can cause it to be unstable?
What is the name of the force that holds protons and neutrons together in the nucleus?
Two nuclei have different mass numbers A1 and A2. Are the two nuclei necessarily isotopes of the same element? Explain.
A material is known to consist entirely of an isotope of calcium, although the particular isotope is not known. From such limited information, which of the following quantities can you specify for
A mixture of two common isotopes of oxygen, oxygen-16 and oxygen-18, is put in a cylindrical chamber that is then spun around its long axis at a very high speed. It is found that one isotope is more
The atomic number of one particular isotope is equal to its mass number. Which isotope is it?
Why do different isotopes of an element have the same chemical properties?
What is meant by the term cold fusion?
Why is magnetic confinement being used in fusion research?
Why are extremely high temperatures effective at causing fusion? What is used to produce such temperatures in a thermonuclear warhead?
If the strong nuclear force had a longer range than it does, what effect (if any) would that have on efforts to harness controlled fusion as an energy source?
Why is a nuclear fusion reaction so difficult to induce?
After a fuel rod in a fission reactor reaches the end of its life cycle (typically 3 years), most of the energy that it produces comes from the fissioning of plutonium-239. How can this be?
There is much more uranium-235 in a typical nuclear power plant than there was in the bomb that destroyed the city of Hiroshima. Why can’t the reactor explode like an atomic bomb?
What are fission fragments, and why are they so dangerous?
Explain how materials that absorb neutrons are used to control nuclear fission chain reactions.
What aspect of nuclear fission makes it possible for a chain reaction to occur? What is the difference between a chain reaction in a bomb and one in a nuclear power plant?
What is the vacuum wavelength of the 0.186 MeV y-ray emitted by radon-226?
The Q-value of a nuclear reaction is a measure of the kinetic energy that the reaction products carry away as a result of the mass that is converted into energy by the nuclear transformation
Using the information given in Section 11.5 and the mass– energy conversion equation, compute the binding energy (in MeV) and the binding energy per nucleon for hydrogen-2 (deuterium).
For nuclei with A > 20 that are not in highly excited states, the protons and neutrons are generally clustered together in an approximately spherical volume whose radius, r, has been empirically
The naturally occurring radioisotopes uranium-238 and uranium-235 have decay chains that end with the stable isotopes lead-206 and lead-207, respectively. Natural minerals such as zircons contain
As a general rule, the radioactivity from a particular radioisotope is considered to be reduced to a safe level after 10 half-lives have elapsed. (Obviously, the initial quantity of the isotope is
Geiger counters are not very accurate when the count rates are very high; they indicate a count rate lower than the actual value. Explain why this is so.
We discussed the deviations in the path of a beam of light after passing through transparent media (refraction) and the role such deviations play in common natural phenomena like rainbows and halos.
According to Table 12.4, the rest mass of an electron is 0.511 MeV/c2. What is the rest mass of a positron?Table 12.4 Mass (MeV/c²) Symbol Family Electron Antiparticle e+ (positron) Particle Name
Distinguish between fermions and bosons in as many different ways as you can.
What is the quark composition of the Δ++ baryon? It has no strangeness, no charm, and no topness or bottomness. Its spin is 3/2.
How many quarks form a baryon? A meson? What is the relationship (if any) between a quark and a lepton (e.g., an electron)?
Describe the kinds of evidence that have led scientists to conclude that quarks exist.
What is a quark? How many different types of quarks are now known? What are some of the basic properties that distinguish these quarks?
In which of the four basic interactions does an electron participate? A neutrino? A proton? A photon?
Give some ways by which physicists classify elementary particles.
Some neutral particles, such as the π0, are their own antiparticles, but not the neutron. In what ways are n and n̅ the same? Speculate on how they might be different.
What is an antiparticle? What may happen when a particle and its anti collide?
What common feature of the electromagnetic and gravitational interactions requires that their carrier (or exchange) particles be massless?
List the four fundamental interactions of Nature, and discuss their relative strengths and effective ranges.
A friend alleges that Buddhist monks residing in monasteries high in the Tibetan Himalayans age more slowly than lobstermen fishing off the coast of Maine. Do you accept her statement as true? Why or
Describe the phenomenon of gravitational time dilation. What experimental or observational evidence exists to support the reality of this prediction of the general theory of relativity?
Do pulsating variable stars, that is, stars that rhythmically expand and contract as a result of thermal instabilities in their atmospheres, generate gravitational waves in this process? Why or why
What are gravitational waves? How are they produced? What evidence is there to substantiate the existence of such radiation?
List three astronomical examples in which the validity of the predictions of general relativity has been demonstrated.
Figure 12.34 shows the trajectory of a comet passing near the Sun. Describe how Newton would explain the deviation in the comet’s path from a straight line. Repeat the explanation as it might be

Showing 600 - 700 of 843