Since
rays
originate
in
a
nuclear
process
,
rather
than
an
process
,
they
tend
to
have
larger
energies
than
x
-
rays
.
Photons
do
not
produce
large
amounts
of
ionization
directly
:
instead
,
they
lose
their
energy
to
electrons
,
which
in
turn
cause
further
secondary
ionization
(
similar
to
-
)
.
gamma
ray
and
x
-
ray
photons
transfer
energy
to
the
electrons
by
3
processes
:
1
-
Photoelectric
Effect
(
Energy
<
0
.
1
MeV
)
2
-
(
Energy
up
to
1
MeV
)
3
-
Pair
Production
(
Energy
>
1
.
02
MeV
)
The
characteristics
of
the
ionization
produced
by
b
-
decay
electrons
and
those
produced
by
gamma
rays
and
x
-
rays
are
the
same
.
So
what
are
the
differences
between
the
effects
of
b
-
particles
and
energetic
photons
?
?
The
high
energy
photons
(
gamma
and
x
-
rays
)
can
penetrate
to
much
greater
depths
(
i
.
e
.
1
.
2
MeV
gamma
rays
from
60
-
Co
decay
can
penetrate
to
about
10
cm
in
tissue
!
!
)
g
-
rays
penetrate
much
deeper
into
matter
because
they
have
no
electric
charge
,
and
therefore
do
not
lose
energy
until
they
produce
or
Compton
electrons
(
and
it's
these
secondary
electrons
that
produce
the
damaging
ionization
)
.
Consequently
,
the
effect
on
internal
organs
will
be
much
greater
due
to
the
deeper
penetration
of
x
-
rays
and
gamma
rays
.
Neutrons
are
and
do
not
produce
ionization
directly
when
passing
through
matter
.
Because
they
have
no
charge
,
they
tend
to
with
atomic
nucleii
rather
than
atomic
electrons
,
and
are
slowed
down
by
elastic
scattering
from
the
nucleii
(
i
.
e
.
collisions
)
.
2
things
happen
:
a
)
The
nucleus
&
moves
.
It
has
a
net
positive
charge
and
can
cause
ionization
.
b
)
Once
the
neutron
has
slowed
down
to
~
1
eV
energy
,
it
has
a
high
probability
of
being
by
a
nucleus
(
often
followed
by
a
gamma
ray
emission
)
.
The
degree
of
penetration
of
a
-
,
b
-
particles
,
and
gamma
rays
depends
on
the
charge
,
mass
,
and
speed
of
the
different
types
of
radiation
,
as
well
as
the
physical
of
the
material
(
i
.
e
.
density
,
etc
.
)
.
Since
a
-
particles
are
heavy
,
slow
-
moving
,
charged
particles
they
can
be
stopped
within
a
cm
of
air
,
or
by
a
thin
sheet
of
paper
.
b
-
particles
are
much
less
massive
and
are
charged
,
so
they
can
travel
a
few
meters
in
air
or
a
few
mm
in
aluminum
before
being
stopped
!
gamma
rays
are
high
speed
photons
with
no
mass
or
charge
and
are
therefore
much
more
penetrating
than
a
-
or
b
-
particles
.
They
can
penetrate
up
to
several
cm
of
high
density
material
such
as
.
The
disintegration
of
a
radioactive
nucleus
within
a
group
of
similar
nucleii
is
a
completely
random
process
.
However
,
after
a
certain
period
of
time
,
half
of
the
parent
(
radioactive
)
nucleii
present
in
the
substance
will
have
decayed
.
After
the
same
period
of
time
,
half
of
the
remaining
nucleii
will
have
and
so
on
.
This
period
of
time
(
where
half
of
the
nucleii
decay
)
is
known
as
the
Half
life
(
T1
/
2
)
.
Ex
.
The
radioactive
isotope
131
-
I
has
a
half
life
of
8
days
.
Regardless
of
how
many
131
-
I
nucleii
are
present
initially
,
only
half
as
many
will
remain
after
8
days
.
Radioactive
half
lives
can
vary
from
a
fraction
of
a
second
to
billions
of
years
!
!
All
organs
within
the
body
will
excrete
or
remove
any
foreign
material
(
e
.
g
.
the
natural
of
medicinal
drugs
)
.
The
Biological
Half
Life
of
any
element
is
the
time
taken
for
-
of
the
original
amount
of
material
present
within
the
body
to
be
removed
or
excreted
.
Hence
,
in
relation
to
radionuclides
used
in
medicine
we
can
define
the
Half
Life
,
which
takes
into
account
BOTH
the
radioactive
and
half
lives
of
the
radionuclide
:
1
/
T
(
effective
)
=
1
/
T
(
/
)
(
radioactive
)
+
1
/
T
(
1
/
2
)
(
biological
)
Note
:
The
Effective
Half
Life
of
any
is
ALWAYS
less
than
either
the
radioactive
or
the
biological
half
lives
on
their
own
.
Watch
the
video
for
the
rest
!