A level AQA physics

random things i find difficult

what colours have the shortest/ longest wavelength

shortest: violet(400nm)

longest: red (700nm)

what are the latent heat types

fusion: solid-liquid

vaporisation:liquid-gas

sublimation:solid-gas

what is gravitational potential at a point

the work done per unit mass in bringing a small test mass from infinity to that point.

what is the electric potential at a point

work done per unit positive charge in bringing a small positive test charge from infinity to that point.

what is modal dispersion

when light enters at different angles, path difference

→ pulse broadening

to fix, use narrower core

(less light lost, increases prob of TIR, less refraction out the core)

what is material dispersion

1 signal, multiple wavelengths, diff wavelengths refract at different angles

→ pulse broadening

to fix, use monochromatic light

describe attraction against nucleon separation graph

repulsive below 0.5fm

attractive 0.5-3fm

strong nuclear force becomes zero over 3fm

what are kaon and pion properties

kaons decay into pions.

what are the fundamental forces and their exchange particles

what is pair production

when high energy photon interacts with mass, releasing an electron and positron

what qualities of transformers are there

use of thicker wires → reduces energy lost to coulomb heating

laminate core → reduces resistance caused by eddy currents

soft iron core → magentises and demagnetises easily

increasing current anywhere in grid → increases efficiency

key facts of alpha radiation

2-10cm penetration in air

strongly ionising

deflectable in mag field

absorbed by paper

used in smoke detectors

key facts of beta

1m penetration in air

weakly ionising

deflectable in mag or electric field

absorbed by 3mm Al

key facts of gamma

infinite range

follows inverse square law

very weak ionising

not deflectable

absorbed by meters of concrete, or 10s of cm of lead

used in: sterilising, radiotherapy,

Technetium-99m pure source, easy to prepare in hospital, short half life

what is keplers third law

T² is proportional to r³