2024 Exam Questions and Answers
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Electron Gun Model Answer - Answer>>- Low voltage supply
heats filament causes thermionic emission/ electrons have
enough energy to leave
- Electrons are repulsed from the cathode (filament) and attracted
towards the anode
- This electric field causes electrons to accelerate
- There is a hole in the anode which creates a beam for electrons
that pass through
- Electrons are then fired through a vacuum (to stop interfering
particles) onto a fluorescent screen
Photo Electric Effect Model Answer - Answer>>- 1 Electron
near the surface of a metal gains 1 photon and gains enough
energy to be liberated
- The work function is the energy needed for the electron to
escape the surface
- increasing intensity will increase the number of photons
- increasing frequency will increase the energy of the photons
- These electrons released are called photoelectrons
- This effect can be explained through E = hf
,PhotoElectric Equation - Answer>>Ekmax = hf - work fucntion
Ekmax = max kinetic energy of freed electrons
hf = energy of photon
work function = the minimum energy to release an electron
Why does the photoelectric effect equation refer to kinetic energy
as maximum kinetic energy? - Answer>>It will not always be an
equal energy transfer:
- Some energy may have been transferred to electrons below the
surface
- Therefore for these electrons to liberate to the surface there will
be heat transfer through collision
- therefore the electrons leaves the surface will less than max
Energy Frequency equation - Answer>>E = hf
E = energy
h = plank's constant
f = frequency
Work function equation - Answer>>Work Function = h x
threshold frequency
Work Function - Answer>>the minimum energy needed to
liberate an electron from a metal atom
Threshold Frequency - Answer>>minimum light frequency
necessary to liberate an electron from a given metal
,Energy is proportional to frequency
Wave Particle Duality Model Answer - Answer>>
Nuclear Binding Energy - Answer>>The energy needed to
separate a nucleus into individual protons and neutrons
E = mc^2
Binding Energy = mass difference x the speed of light^2
How to calculate nuclear binding energy from a nuclear decay
equation? - Answer>>Th -> Ra + a
Mass of Th nuclear-(Mass of Ra nuclear + mass of alpha particle)
Convert u to kg
Multiply by speed of light^2 E = mc^2
Convert to Mev
How to convert u to kg - Answer>>kg / 1.6605x10^-27
How to convert kg to u - Answer>>kg / 1.6605x10^-27
What is 1 u? - Answer>>1.6605x10^-27kg
Converting u to Mev - Answer>>u x 931.5
Converting Mev to u - Answer>>Mev / 931.5
, Electron Volt - Answer>>The energy given to an electron by
accelerating it through 1 volt of electric potential difference. 1.6 x
10-19 joules.
Model answer for Fission - Answer>>- Strong nuclear forces
that hold the nucleus together only act a small distance
- When a big nucleus absorbs a neutron it deforms the nucleus
- The electrostatic repulsion between protons becomes greater
than the strong nuclear force
- it then splits (random)
Chain Reaction - Answer>>As a fission reaction splits it
produces 3 neutrons which can go on to split 3 other neutrons
creating an exponential chain reaction
Model answer for fusion - Answer>>- two light nuclei join
together to make a heavier nucleus
- This gives out more energy per nucleon than than fission as the
increase in binding energy is much larger for fusion reactors
Advantages of Fusion over Fission - Answer>>- Power output is
greater
- Raw materials are cheap and available (hydrogen in water)
- No radioactive waster is produced directly
Why Fusion is hard to do? - Answer>>The need for:
- enormous pressure
- enormous temperatures