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alpha particle

2 protons and 2 neutrons

alpha radiation

most ionising

shortest range through air

stopped by a sheet of paper

beta radiation

less ionising than alpha but more than gamma

longer range through air than alpha but shorter than gamma

stopped by a sheet of aluminium

beta -

an electron

released when a neutron turns into a proton

beta +

a positron

released when a proton turns into a neutron

gamma radiation

least ionising

longest range through air

stopped by a block of lead

radioactive decay

occurs when an unstable nucleus tries to become stable by releasing alpha beta or gamma

initial element

new element + type of radiation

dangers of radiation

radiation ionises cells

could damage dna in the cells

leads to mutation

leads to cancer

half life

time taken for half of the radioactive nuclei in a substance to decay

irradiation

object is exposed to the radiation from outside the body

contamination

object becomes radioactive itself

nuclear fission

a nucleus splits into 2 smaller daughter nuclei

when this happens energy is released

control rods

moveable rods that can absorb neutrons to control the rate of fusion

moderators

used to slow down neutrons so the uranium rods can capture them

this increases the rate of fission

nuclear fusion

a process where 2 small nuclei join together to form one big nucleus

some of the mass is coverted to energy

two conditions for nuclear fusion to occur

extremely high temperatures

extremely high pressures

rutherfords gold foil experiment

gave evidence for the nuclear model

rutherfords - most of the alpha particles went through

most of the atom must be empty space

rutherfords - some of the alpha particles were detected at slight angles and very few at angles reater than 90

there is concentrated mass in the centre of the atom - the nucleus

background radiation

radiation that is always present in a particular area

radon rocks

releases radon gas which is highly ionising

geiger muller tube

measures radioactivity

countrate

measurement of how radioactive an object is

transverse wave

every point on the wave vibrates at 90 degrees to the direction of energy transfer

longitudinal wave

every point on the wave vibrates parallel to the direction of energy transfer

wavelength

distance from any point on a wave to where that exact point occurs again

frequency (Hz)

number of waves passing a point every second

time period

time taken to complete one full wave

time period equation

time period = 1/frequency

wave speed equation (m/s)

v = f x λ

how to answer calculations questions (vess)

values

equation

substitute

solve

infrasound

frequencies less than 20 Hz

ultrasound

frequencies more than 20000 Hz

speed equation

speed = distance / time

em spectrum

radiowaves

microwaves

infrared

visible light

ultraviolet

x rays

gamma rays

ionising waves

ultraviolet

x rays

gamma rays

uses of gamma rays

sterilising medical equipment

radiotherapy

uses of x rays

medical imaging

airport security

uses of ultraviolet

bank security

visible light

allows us to see

uses of infrared

short range communication

night vision

cooking

uses of microwaves

long range communication

cooking

refraction

when a wave goes from one medium to another and changes speed and direction

when a wave slows down

bends towards the normal

angle of i > angle of r

when a wave speeds up

bends away from the normal

angle of r > angle of i

lens

piece of glass used to refract light

types of lenses

convex and concave

convex lens rules

any ray travelling parallel to the principle axis gets refracted thought the focal point

any ray travelling through the centre of the lens does not get refracted at all

how to describe ray diagram image

inverted or upright

magnified, diminished or same size

real or virtual

total internal reflection

when a ray travels from a high dense medium to a low dense medium

critical angle

angle of incidence where the angle of refraction is 90

absorption

when the energy from the wave is transferred to the boundary

transmission

when the wave passes through the boundary

object staying at constant temperature

rate of energy being absorbed is equal to the rate of energy being emitted

object getting hotter

rate of energy being absorbed is greater than the rate of energy being emitted

object getting colder

rate of energy being emitted is greater than rate of energy being absorbed

s waves

transverse

p waves

longitudinal

s waves travel

through solids but not liquids

p waves travel

through solids and liquids

scalars

has magnitude

vectors

has magnitude and direction

acceleration

the rate of change in velocity

velocity time graphs

show how fast objects travel in a set period of time

distance time graphs

show how the distance travelled by an object changes over time

distance time graphs gradient

shows speed

velocity time graphs gradient

shows acceleration

momentum

depends on an objects mass and velocity

total momentum before collision

equals total momentum after collision

impulse

change in momentum

stopping distance equation

thinking distance + braking distance

stopping distance

the total distance travelled during the time it takes for a car to stop in response to an emergency

thinking distance

the distance travelled in the time it takes the driver to react

braking distance

the distance travelled under braking force

opposite poles

attract

like poles

repel

non contact force

a force that acts between objects that are not touching

non uniform field

field strength is not the same everywhere

uniform field

field strength is the same everywhere

three magnetic metals

iron nickel cobalt

permanent magnets

always have a magnetic field around them

temporary / induced magnets

only have a magnetic field when they are placed in another magnets magnetic field

electromagnets

only have a magnet field when there is a current flowing through them

ways to increase the strength of an electromagnet

increase current 

increase number of turns in coil

add an iron core

force on wire calculation

f = b x i x l

magnetic field points

north to south

current goes from

positive to negative