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Question
Which of the following is essential for the laser action to occur between two energy levels of an atom?A) the lower level is metastable
B) there are more atoms in the upper level than in the lower level
C) there are more atoms in the lower level than in the upper level
D) the lower level is the ground state
E) the lasing material is a gas
Answer
This answer is hidden. It contains 1 characters.
Related questions
Q:
The intensity of the microwave background radiation, a remnant of the big bang:
A) is greatest in directions toward the center of the galaxy
B) is least in directions toward the center of the galaxy
C) is proportional to the reciprocal of the distance from us
D) is proportional to the square of the distance from us
E) is nearly the same in all directions
Q:
The velocities of distant objects in the universe indicate that the time elapsed since the big bang is about:
A) 105y
B) 1010y
C) 1015y
D) 1020y
E) 1025y
Q:
In terms of quark content a beta decay can be written:
Q:
The quark content of a proton is:
A) uuu
B) uud
C) udd
D) ddd
E) uds
Q:
The up quark u has charge +2e/3 and strangeness 0; the down quark d has charge -e/3 and strangeness 0; the strange quark s has charge -e/3 and strangeness -1. This means there can be no baryon with:A) charge 0 and strangeness 0B) charge -eand strangeness -1C) charge +eand strangeness -1D) charge +eand strangeness -2E) charge 0 and strangeness -2
Q:
A baryon is a combination of:
A) three quarks
B) two quarks and an antiquark
C) one quark and two antiquarks
D) one quark and one antiquark
E) two quarks
Q:
Any meson is a combination of:
A) three quarks
B) two quarks and an antiquark
C) one quark and two antiquarks
D) one quark and one antiquark
E) two quarks
Q:
Quarks are the constituents of:
A) all particles
B) all leptons
C) all strongly interacting particles
D) only strange particles
E) only mesons
Q:
The color theory explains why quarks:
A) form particles in pairs and triplets
B) have charge that is a multiple of e/3
C) have spin
D) have mass
E) none of the above
Q:
The two basic interactions that have finite ranges are:
A) electromagnetic and gravitational
B) electromagnetic and strong
C) electromagnetic and weak
D) gravitational and weak
E) weak and strong
Q:
Strangeness is conserved in:
A) all particle decays
B) no particle decays
C) all weak particle decays
D) all strong particle decays
E) some strong particle decays
Q:
When a kaon decays via the strong interaction the products must include a:
A) baryon
B) lepton
C) strange particle
D) electron
E) neutrino
Q:
Two baryons interact to produce pions only, the original baryons disappearing. One of the baryons must have been:
A) a proton
B) an omega minus
C) a sigma
D) an antiparticle
E) none of these
Q:
A neutral lepton cannot decay into two neutrinos. Of the following conservation laws, which would be violated if it did?
A) Energy
B) Baryon number
C) Linear Momentum
D) Angular momentum
E) None of the above
Q:
An electron participates in:
A) the electromagnetic and weak forces only
B) the strong and weak forces only
C) the electromagnetic and gravitational forces only
D) the electromagnetic, gravitational, and weak forces only
E) the electromagnetic, gravitational, and strong forces only
Q:
An example of a fermion is a:
A) photon
B) pion
C) neutrino
D) kaon
E) none of these
Q:
A particle with spin angular momentum is called a:A) leptonB) hadronC) fermionD) bosonE) electron
Q:
The microwave background radiation is a result of the big bang. The big bang also resulted in a uniform distribution of background:
A) electrons
B) quarks
C) gluons
D) neutrinos
E) atoms
Q:
Compared to fusion in a tokamak, laser fusion makes use of:
A) smaller particle number densities
B) greater particle number densities
C) longer confinement times
D) higher temperatures
E) lower temperatures
Q:
For a controlled nuclear fusion reaction, one needs:
A) high number density nand high temperature T
B) high number density nand low temperatureT
C) low number density nand high temperature T
D) low number density nand low temperature T
E) high number density nand temperature T = 0 K
Q:
The first step of the proton-proton cycle is:
Q:
Nuclear fusion in the Sun is increasing its supply of:
A) hydrogen
B) helium
C) nucleons
D) positrons
E) neutrons
Q:
The purpose of a moderator in a nuclear reactor is to:
A) provide neutrons for the fission process
B) slow down fast neutrons to increase the probability of capture by uranium
C) absorb dangerous gamma radiation
D) shield the reactor operator from dangerous radiation
E) none of the above
Q:
In the normal operation of a nuclear reactor:
A) control rods are adjusted so the reactor is subcritical
B) control rods are adjusted so the reactor is critical
C) the moderating fluid is drained
D) the moderating fluid is continually recycled
E) none of the above
Q:
The energy supplied by a thermal neutron in a fission event is essentially its:
A) excitation energy
B) binding energy
C) kinetic energy
D) rest energy
E) electric potential energy
Q:
When 236U fissions the fragments are:
A) always 140Xe and94Sr
B) always identical
C) never 140Xe and 94Sr
D) never identical
E) none of the above
Q:
A certain nucleus, after absorbing a neutron, emits a and then splits into two alpha particles. The (A, Z) of the original nucleus must have been:A) 6, 2B) 6, 3C) 7, 2D) 7, 3E) 8, 4
Q:
Radioactive polonium, 214Po (Z= 84), decays by alpha emission to:
A) 214Po (Z= 84)
B) 210Pb (Z= 82)
C) 214At (Z= 85)
D) 218Po (Z= 84)
E) 210Bi (Z= 83)
Q:
Rank the following collections of particles according to the total binding energy of all the particles in each collection, least to greatest. collection 1: 244Pu (Z = 94) nucleus alone collection 2: 240U (Z = 92) nucleus, particle collection 3: 240U (Z = 92) nucleus, two separated protons, two separated neutronsA) 1,2,3B) 3,2,1C) 2,1,3D) 1,3,2E) 2,3,1
Q:
Bombardment of 28Si (Z= 14) with alpha particles may produce:
A) a proton and 31P (Z= 15)
B) hydrogen and 32S (Z= 16)
C) a deuteron and 27Al (Z= 13)
D) helium and 31P (Z= 15)
E) 35Cl (Z= 17)