PHY102 HW 12

A certain radioactive isotope placed near a Geiger counter registers 160 counts per second. Eight hours later, the counter registers 10 counts per second. What is the half-life of the isotope? A. 8 hours B. 6 hours C. 4 hours D. 2 hours E. none of these

2 hours

Control is exercised in a nuclear reactor by A. absorbing excess neutrons with control rods. B. emitting fast neutrons with a moderator. C. both of these D. none of these

absorbing excess neutrons with control rods

True or False: If a 20 kg brick is made entirely of radioactive atoms of half-life 5 days, at the end of 5 days this brick will have a mass of 10 kg.

false

True or False: If half of a radioactive substance decays in the first 10 s, the other half will decay in the next 10 s. A. True B. False

false

A chain reaction grows when the average number of liberated neutrons that go on to cause further fissions is A. zero. B. less than one. C. one. D. greater than one.

greater than one

Nuclei which are all isotopes of an element all have the same A. number of protons. B. mass. C. number of nucleons. D. number of neutrons.

number of protons

Carbon dating requires that the object being tested contain A. organic material. B. inorganic material. C. charcoal. D. sugar molecules. E. none of these

organic material

The nucleus with the greatest mass is A. hydrogen. B. iron. C. lead. D. uranium. E. plutonium.

plutonium

A gram of radioactive material has a half-life of one year. After 4 years, how much radioactive material will be left? A. 0 g B. 1/2 g C. 1/4 g D. 1/8 g E. 1/16 g

1/16 g

The half-life of an isotope is one day. At the end of two days the amount that remains is A. none. B. one-half. C. one-quarter. D. one-eighth. E. none of these

1/4

The half-life on an isotope is one day. At the end of three days, how much of the isotope remains? A. none B. one-half C. one-quarter D. one-eighth E. none of these

1/8

When radium (atomic number = 88) emits an alpha particle, the resulting nucleus has atomic number A. 86. B. 88. C. 90. D. 92. E. none of these

86

A device that is used primarily to detect nuclear radiation is a A. synchrotron. B. linear accelerator. C. cyclotron. D. Geiger counter. E. All of the above choices are correct.

Geiger counter

An element will decay to an element with higher atomic number in the periodic table if it emits A. a beta particle. B. a gamma ray. C. a proton. D. an alpha particle. E. none of these

a beta particle

If an alpha particle and a beta particle have the same energy, which particle will penetrate farther into an object? A. alpha particle B. beta particle C. They both penetrate the same distance. D. It depends on what atom they decayed from.

beta particle

When an alpha particle is ejected from a nucleus, the nucleus then has less A. mass. B. charge. C. both of these D. neither of these

both of these

In the fissioning of uranium, a chain reaction is caused by A. the enormous energy release. B. the kinetic energy of the decay products. C. ejected neutrons. D. the conversion of mass to energy. E. none of these

ejected neutrons

What makes an element distinct? A. the number of protons B. the number of neutrons C. the number of electrons D. the total mass of all the particles E. none of these

the number of protons