phys. final

In a decay of 90Th 232 by emission of an alpha particle, the daughter nucleus will be

88Ra228.

A nucleus undergoes radioactive decay, emitting a gamma ray. Which of the following statements is true?

Both daughter and parent nuclei have the same atomic number

Which of the following mechanisms can change the half-life of radioactive nuclei?

None of these.

What is the source of the energy released in nuclear reactions?

The conversion of mass to energy.

In nuclear fission,

a nucleus is split into two less massive nuclei.

In all nuclear reactions,

all of these

Energy released in a nuclear fission process is produced by

conversion of some mass to energy.

A "gamma" ray is

electromagnetic radiation

The energy radiated by the sun has as its primary origin energy produced by reactions.

fusion

The three types of nuclear radiation are

gamma, beta, alpha.

Generally, the number of neutrons present in nuclei that are fission fragments is ________ the number of neutrons of corresponding nuclei of stable isotopes.

greater than

The substance that comes from a nuclear reactor which can be used to generate power is

high-pressure steam.

When a nucleus undergoes alpha decay, the daughter element always has

less charge than the parent.

A deuterium nucleus and a tritium nucleus react to yield one alpha particle, a neutron, and energy. For this reaction, the sum of the masses of reaction products after the reaction is __________ the sum of the masses of particles before the reaction.

less than

Momentum and energy from focused laser beams can be used in nuclear fusion. This has an advantage over magnetic confinement reactors in that

light cannot be melted, so its pressure can confine the reaction

The primary reason that nuclear fusion has proven difficult to adapt for commercial power generation is that

nuclei repel each other due to their positive charges

The purpose of the moderator in a reactor is to

slow neutrons down so that they will be more likely to initiate fission reactions

Neutrons were discovered by James Chadwick by observing the behavior of

the collision after-effects of protons emerging from paraffin.

The number of protons in the nucleus of an atom determines

the density of the nucleus.

Consider two different samples of radioactive isotopes, one naturally occurring and the other artificially produced. If the samples have the same number of nuclei, then

the one with the shorter half-life is likely more dangerous.

In a nuclear reactor, "chain reaction" refers primarily to

the process by which the fission of one nucleus causes other nuclei to undergo fission.

A sample of U 235 that is below the critical mass will not sustain a chain reaction because

too many neutrons escape through the surface of the sample without initiating fission.

A feature of the nuclear reactor at Chernobyl that contributed to the magnitude of the accident there was that

water was used only as a coolant, not a moderator