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Flashcards in Radioactivity (Sec G) Deck (13)
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1
Q

What is the meaning of atomic number & mass number?

A
  • Atomic number: No. of protons in the nucleus

- Atomic mass: No. of protons + no. of neutrons

2
Q

Name some radioactive elements

A
  • Francium (Fr)
  • Plutonium (Pu)
  • Uranium (U)
  • Technetium (Tc)
  • Radium (Ra)
3
Q

What are alpha & beta particles?

A
  • Alpha particles: Helium nuclei ejected from unstable nuclei. Heavily ionising, short range (10 cm), stop easily
  • Beta particles: Fast moving electrons ejected from unstable nuclei. Less ionising, travel more, stopped by Al
4
Q

What are gamma rays?

A

Gamma rays are photons of high energy EM waves. Takes a lot to stop them (10 cm of Pb, to be precise). Emit ionising radiation by interacting with nearby atoms.

5
Q

Tell me about radioactive decay

A

Isotopes of elements will randomly decay, emitting radiation. Alpha & beta emissions cause a change in atomic number. Decay equations must balance

6
Q

How can radiation be detected?

A
  • Photographic film: Becomes fogged when exposed

- Geiger-Muller tube: When ionising radiation enters the tube, it ionises gases inside, allowing current to pass

7
Q

Where does background radiation come from?

A
  • Rocks: Slow decay of isotopes of uranium
  • Cosmic rays: Explosions of stars
  • Medical treatment: Diagnosis & treatment of illnesses
  • Nuclear power: Weapon testing, leaks
8
Q

What is meant by the term “half-life”?

A

The half-life of an isotope is the time taken for half the original number of unstable nuclei to decay

9
Q

Where can radioactivity be applied?

A
  • Medicine: Tracers, treatment by killing cells
  • Sterilisation: Kills microbes on equipment/food
  • Non-medical tracers: Seeing flow of chemicals in industry
  • Radioactive dating: Looking at how long ago stuff died
10
Q

What were the observations from Geiger & Mardsen’s experiment?

A
  • Most alpha particles passed through
  • Some were deflected
  • Very few bounced back
11
Q

What is the meaning of the term ‘fissile’?

A

It refers to isotopes which can be split into lighter elements easily

12
Q

What affects the amount of deflection of alpha particles shot through a sheet of metal?

A
  • Speed of particles: Faster = smaller angles of deflection
  • Nuclear charge: Highly charged = more deflections
  • How close the particle gets to the nucleus
13
Q

What is the unit of radioactive decay?

A

Becquerel (Bq)

1 Bq = 1 decay per second