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6. How do nuclei become more stable?

  • Undergo fission
  • Emit alpha, beta and gamma radiation
  • Emit alpha and beta radiation

7. Why is a vacuum needed for the alpha scattering experiment?

  • Alpha particles scatter off of air particles
  • Alpha particles would be slowed down
  • Alpha radiation might come from the air particles

8. What is the half life of a nucleus?

  • Number of nuclei left after half a minute
  • Time for activity to decrease by a half
  • Time for activity to decrease to zero

9. What is understood about the atom when some alpha particles deflect by more than 90 degrees

  • The nucleus is negative
  • The nucleus is positive
  • The nucleus of gold is larger than alpha radiation

10. What is understood about the atom when most alpha particles pass through gold foil

  • Most of the mass of an atom is concentrated in the nucleus
  • Most of the mass of an atom is spread out
  • Nuclei are positive

11. Why do substances for medical tracers have a 6 hour half life?

  • Radioactive substance will be digested before it fully decays
  • Stable enough to make measurements and decays away after use
  • Short enough that radiation won't reach sensitive parts of the body

12. Why do nuclei emit photons?

  • They form a more stable isotope
  • They have too much energy, which photons take away
  • Makes them change into another element

13. Why is alpha radiation not used for medical tracers?

  • Can't penetrate the skin
  • Not very stable
  • Emits too much energy

14. What is the range of a beta particle?

  • Up to a meter
  • A few cm
  • Infinite

15. What are the effects of ionisation on the body?

  • Destroys cell membrane and damages DNA
  • Destroys cell membrane but DNA is unaffected
  • Damages DNA but cell membrane is unaffected

16. In radioactivity what does the symbol lambda stand for?

  • Wavelength
  • Probability that a nucleus decays per second
  • Probability that a nucleus decays per kilogram

17. Before Rutherford's experiment what was the popular structure for the atom?

  • Quantum
  • Plum pudding
  • Nuclear