AQA Physics Particles and Radiation notes

MATTER AND RADIATION
structure of the atom
charge C Relative
charge Mass
kg Relative mass



Every atom contains :



proton +1.60×10-19 I 1.67131×10-27 I


a
positively charged nucleus composed of
protons and neutrons
•




neutron O O 1.67151×10-27 I


↳ nucleus contains most of the mass of the atom 3'
1.60×10-19
.




electron
-



-
-
I 9.11 x 10 O .
0005


•
electrons that surround the nucleus


electrostatic force of attraction between them and nucleus
↳ electrons are held in the atom
by the the .




Nucleon : a
proton or neutron in the nucleus




Isotopes
Isotopes atoms with the number of protons but different number of neutrons
°


are same .




.
2 =
Proton number / Atomic number A
X chemical
-
A =
Nucleon number / Mass number 2 symbol
no .
of neutrons = A -
2

Each of nucleus nuclide and labelled notation
type is a is
using
the isotope
.




Specific charge charge ,
C


Q
Specific charge of
charged particle defined its
charge divided
by its mass
(
l
'

as

kg
a is
-


=

M

Electron has the
.




largest specific charge of
any particle mass
,
kg


The nuclear force
strong
Force that the electrostatic force of between the
repulsion protons the nucleus and keeps the
protons and neutrons
together
'


overcomes in .




does not
↳ nuclei of stable isotope disintegrate
'




. .
a .




has of femto meters ( fm ) Ism
-




short 3 4 Ifm 10
range
a
- -
=

,




has effect between 2 it does between 2 neutrons
-

same
protons as or a
proton and a neutron



.
an attractive force from 3 -
4 fm down to 0.5 fm .
At smaller
separations ,
it is a
repulsive force to
prevent neutrons and
protons being

into each other
pushed




I|
force
infinite decreases increases
; range
as
range
I
electrostatic force
§



distacneanerterom
I strong nuclear force
is
L,

, Radioactive
decay
Naturally occurring
radioactive
isotopes release 3
types of radiation
-


:




i ) Alpha radiation

consists of
alpha particles each and It
which
comprise
2
protons 2 neutrons
•

.




A A -4 4
X s Y + a
Z 2
z -
2


.


product nucleus
belongs to a different element Y .




2) Beta radiation

YB ( )
-




B beta
particle
:

consists of fast electrons or
moving
'
-
-

.




neutron
. beta particle created and emitted
instantly when a in the nucleus
changes into a
proton
↳
an
antiparticle with no
charge antineutrino ( t ) is emitted .




,




this ( neutron ) to nuclei that neutrons
.




change >
proton happens have too
many
.




Az X s
zany +
:B + i




3) Gamma radiation V

emitted unstable
-



electromagnetic radiation
by an nucleus


.
can
pass through thick metal
plates
.
no mass
,
no
charge
. emitted
by a nucleus with too much
energy , following an
alpha or beta emission




The existence of the neutrino was
hypothesised to account for conservation of
energy
in beta
decay .




↳ scientists found that beta particles were released with kinetic
energies up to a maximum that
depended on the
isotope although
,




each unstable nucleus lost certain amount of the
a
energy
in
process .




conserved ( & )
away by
not of it carried neutrinos
mystery particles antineutrinos
↳ either
energy
was in the
change or some were




Electromagnetic waves



l 108ms
speed of all
electromagnetic the
speed of
light 3.00 )
'
in vacuum is x
-


waves a
-


c
,




electric field




n
\



C
.




A =

f 9
field
magnetic
-




nm = 10 m



.
direction of wave


that
.




electromagnetic wave consists of an electric wave and a
magnetic wave travel
together
and vibrate : at
right angles to each other and to the direction of travel
;


with each other
in
phase .