Which nuclear emission has the greatest mass and the least penetrating power?

A. an alpha particle
Correct! Alpha particles have a mass of 4 and can be stopped by a sheet of paper.

B. a beta particle
Incorrect. Beta particles have a mass of nearly zero and need at least aluminum foil to be stopped.

C. a gamma ray
Incorrect. Gamma rays have a mass of zero and the highest penetrating power.

D. a neutron
Incorrect. Neutrons have a mass of 1 which is less than alpha particles.

A 3 cm thick piece of cardboard placed over a radiation source would be most effective in protecting against which type of radiation?

A. alpha
Correct! Alpha particles can be stopped by paper so a 3cm thick piece of cardboard should stop all alpha particles.

B. beta
Incorrect. The cardboard might stop some of the beta particles but it would not be as effective as stopping alpha particles.

C. gamma
Incorrect. This would do little to stop gamma rays.

D. X-ray
Incorrect. This would do little to stop X-rays.

Assuming that the radiation source above emits beta particles, as the particles pass between the charged plates they will —

A. be deflected from one plate to the other throughout the tube
Incorrect. Beta particles have a negative charge so they would not be deflected toward the negative plate.

B. be deflected upward
Correct! Beta particles have a negative charge so they would be attracted to the positive plate causing them to deflect upward.

C. be deflected downward
Incorrect. Beta particles have a negative charge so they would not be deflected toward the negative plate.

D. pass straight through
Incorrect. Beta particles have a negative charge so be attracted to the positive plate.

Which type of radiation is identical in mass and charge to a helium nucleus?

A. alpha
Correct! Alpha radiation has a mass of 4 and a charge of +2 which is the same as a helium nucleus.

B. beta
Incorrect. Beta radiation has a mass of 0 and a charge of -1 which is the same as an electron.

C. proton
Incorrect. A proton has a mass of 1 and a charge of +1 which is the same as a hydrogen atom.

D. gamma
Incorrect. A gamma ray has a mass of 0 and a charge of 0.

Which of the three types of radiation will penetrate the paper and wood?

A. alpha, beta, and gamma
Incorrect. Alpha would be stopped by the paper and most of the beta would be stopped by the wood.

B. alpha and beta only
Incorrect. Alpha would be stopped by the paper and most of the beta would be stopped by the wood.

C. gamma only
Correct! Gamma would be unaffected by the paper and wood. In order to stop gamma you would need a thick piece of lead or concrete.

D. beta only
Incorrect. Gamma would penetrate the paper and wood.