IGCSE Physics - Atomic Physics Flashcards
Electron Mass
(1/1840) approx. 0
Proton Mass
1
Neutron Mass
1
Electron Charge
-1
Proton Charge
`+1
Neutron Charge
0
Describe Rutherford’s experiment
Alpha particles (charge +2) were fired at a thin
sheet of gold foil
Most particles went straight through
Some particles were deflected by small angles
(< 90º)
A few particles were deflected by large angles
(> 90º)
What are the conclusions of Rutherford’s experiment?
- Most of an atom is empty space
- The nucleus has a positive charge
- Most of the mass is concentrated in
the nucleus
What is nuclear fission?
When a large and unstable nucleus splits to form two smaller nuclei, neutrons and energy.
What is nuclear fusion?
When two small nuclei fuse to form a heavier nucleus and release energy.
Describe (Alpha) α radiation.
-1 particle consists of 2 protons and 2
neutrons (same as a helium nucleus)
- Highly ionizing
- Weakly penetrating
Describe (Beta) ß radiation.
- 1 particle consists of a single electron
- Medium ionizing effect
- Medium penetration
Describe (Gamma) γ radiation.
- Weakly ionizing
- Highly penetrating
- Electromagnetic radiation (no
particles)
How can radiation be detected?
- Photographic film
- Geiger-Muller tubes
How does photographic film work?
The film is white; as it absorbs radiation it darkens.
Describe the action of Geiger-Muller tubes
They are tubes which transmit an electric pulse every time radiation is absorbed, producing a clicking sound
What is background radiation?
Weak radiation from external sources which is always present.
Define half life
Half life is the time taken for the number of radioactive nuclei to halve, or the time taken for the count rate/activity to halve.
What are some safety precautions when using radiation?
- Minimize exposure time
- Keep as much distance from the source as possible
- Use shielding eg. lead
