Physic IB unit 12

A pure sample of a radioactive nuclide contains N₀ atoms at time t = 0. At time t, there are N atoms of the nuclide remaining in the sample. The half-life of the nuclide is t_1/2.

What is the decay rate of this sample proportional to?

• N

• N₀ - N

• t

• t _1/2

The half-life of a radioactive nuclide is 8.0 s. The initial activity of a pure sample of the nuclide is 10 000 Bq. What is the approximate activity of the sample after 4.0 s?

• 2500 Bq

• 5000 Bq

• 7100 Bq

• 7500 Bq

The diameter of a silver-108 (¹⁰⁸₄₇Ag) nucleus is approximately three times that of the diameter of a nucleus of

• ⁴₂He

• ⁷₂Li

• ¹¹₅Be

• ²⁰₁₀Ne

The graphs show the variation with distance x of the square of the amplitude Ψ² of the wave function of a particle. Which graph corresponds to a particle with the largest uncertainty in momentum?

• A

• B

• C

• D

Photons of discrete energy are emitted during gamma decay. This is evidence for

• atomic energy levels.

• nuclear energy levels.

• pair annihilation.

• quantum tunneling.

A particle of fixed energy is close to a potential barrier.

Which changes to the width of the barrier and to the height of the barrier will always make the tunnelling probability greater?

• A

• B

• C

• D

An electron of initial energy E tunnels through a potential barrier. What is the energy of the electron after tunnelling?

• greater than E

• E

• less than E

• zero

Electron capture can be represented by the equation

p + e– → X + Y.

What are X and Y?

• A

• B

• C

• D

Nuclear density

• is constant because the volume of a nucleus is proportional to its nucleon number.

• is constant because the volume of a nucleus is proportional to its proton number.

• depends on the nucleon number of the nucleus.

• depends on the proton number of the nucleus.

A particular radioactive substance decays and emits both β+ particles and neutrinos. Which describes the nature of the energy spectrum of the β+ particles and the nature of the energy spectrum of the neutrinos?

• A

• B

• C

• D