Questions Flashcards
(9 cards)
Why is a moderator used?
neutrons have to be slowed down; because the probability of fission is greater with neutrons of energy 1eV; neutrons lose energy by colliding with atoms in the moderator
How do polarised sunglasses reduce glare
The light from the water is horizontally polarised;
Sunglasses have a vertical plane of polarisation;
Hence the transmitted intensity is lower because the lenses absorb much of the reflected light
Dangers of nuclear energy (3)
Meltdown risk, nuclear weapon production, radiation leak.
Why must uranium be enriched?
Uranium 238 is more common than 235. U-235 is better for fission, and U-238 absorbs neutrons (slowing down fission).
Photoelectric effect (4)
Light consists of photons
Each photon has energy E=hf
A certain amount of energy is required to eject an electron from a metal
If hf less than this energy, no electrons are emitted.
Obtaining atomic spectra (3)
Apply p.d across a gas discharge tube.
Shine light through a diffraction grating.
Observe diffracted light to find out wavelength.
Findings of Davisson-Germer
Beam of electrons produced by filament scattered of nickel crystal
Electron detector showed that intensity was sometime at a maximum and sometimes at a minimum
Suggesting that the electrons were interfering like waves.
Electron in a box model
The de Broglie wavelengths are the wavelengths of the standing waves permitted by the box’s boundary conditions.
Assumptions of kinetic theory (5)
Newton's laws of motion apply Random motion No intermolecular forces Point particles Collisions are elastic and instantaneous
