Modern
Physics
Classical
Mechanics
  Galileo
and
Newton
assumed
that
the
laws
of
physics
applied
in
all
iner9al
frames,
frames
of
reference
that
are
NOT
accelera9ng
or
rota9ng,
and
they
were
right.
Even
though
they
were
both
aware
that
mo9on
was
rela9ve,
they
believed
that
the
laws
would
apply
regardless.
Space
was
believed
to
be
fixed
so
9me
and
distances
were
constants.
  Nineteenth
century
scien9sts
believe
that
there
was
a
transparent
background,
“ether”,
of
space
that
light
traveled
in.
So
they
assumed
that
since
mo9on
was
rela9ve
so
too
would
the
speed
of
light
be
rela9ve.
They
believed
that
the
speed
that
Maxwell
calculated
was
rela9ve
to
the
ether
of
space.
 Example:
My
mo9on
on
Earth
measured
by
you
verses
my
mo9on
measured
by
a
person
on
the
moon.
Einstein’s
Theory
of
Special
Rela9vity
 However,
in
the
late
19th
century
James
Maxwell
came
up
with
the
speed
of
all
electromagne9c
radia9on
to
be
a
constant
of
c
=
3X108
m/s
in
all
reference
frames.
In
other
words,
they
proved
that
the
speed
of
light
was
NOT
rela9ve.
It
did
not
seem
to
follow
the
law
of
rela9vity.
Michelson‐
Morley
did
experiments
that
proved
light’s
speed
did
not
change
no
maWer
what
the
iner9al
reference
frame
and
this
was
referred
to
as
the
“null
result”.
Postulates
of
the
Special
Theory
of
Rela9vity
 In
1905,
Einstein
proposed
that
there
was
no
absolute
reference
frame,
“ether”,
that
was
at
rest
in
the
fabric
of
space.
Space
was
not
the
constant.
He
proposed
two
postulates:
 1st(the
rela9vity
principle)
 The
laws
of
physics
have
the
same
form
in
all
iner9al
reference
frames.
 2nd(constancy
of
the
speed
of
light)
 Light
propagates
through
empty
space
with
a
definite
speed
c
independent
of
the
speed
of
the
source
or
observer.
Time
Dila9on
*Δt =
Δt o
2
v
1− 2
c
= Δt 0γ γ =
1
v2
1− 2
c
This factor so common
in relativity that we give it a special symbol
 One
consequence
of
special
rela9vity
is
that
9me
is
no
longer
a
constant
and
depends
on
the
frame
€
of
reference.
 Time
dila9on
says
that
clocks
moving
rela9ve
to
an
observer
are
measured
by
that
observer
to
run
more
slowly,
as
compared
to
clocks
at
rest
rela9ve
to
the
observer.
Notice that as you approach
the speed of light the
denominator of the fraction
approaches zero and the time
dilation approaches infinity! Length
Contrac9on
v2
*L = Lo 1− 2
c
Lo
or L =
γ
  Not
only
does
9me
dilate
but
lengths
and
distances
shrink.
Since
c
is
constant
and
the
space
ship
measures
a
shorter
9me
then
the
distance
must
be
short
also,
c
(v)=x/t,
for
the
speed
of
light
to
remain
constant.
  The
length
of
an
object
is
measured
to
be
shorter
when
it
is
moving
rela9ve
to
the
observer
that
when
it
is
at
rest.
However,
this
is
only
when
the
object
and
observer
are
moving
parallel
to
each
other
NOT
perpendicular.
A rocket is moving away from the Earth at a speed of .8c. If an
hour passes on the clock on the rocket, how much time would have
passed on a clock on Earth? slower, at about 0.6 times the rate of the clocks at rest
Rela9vis9c
Momentum
and
Mass
 As
a
par9cle
speeds
up
its
momentum
and
mass
increase.
According
to
the
following
equa9ons:
p = γmov
and
mrel = γmo
 However,
be
careful,
a
mass
does
not
acquire
more
par9cles
or
molecules
as
it
speeds
up.
Most
physicists
believe
it
only
appears
to.
Mass
and
Energy
2
*E=mc
*1u = 931.5 MeV
€
−13
1MeV =1.60 ×10 J
 In
his
famous
equa9on
Einstein
deduced
that
because
of
special
rela9vity
that
the
old
equa9on
for
kine9c
energy
would
have
to
be
changed
in
order
to
account
for
rela9vis9c
considera9ons
and
derived
mathema9cally
his
equa9on
that
linked
energy
and
mass.
What is the equivalent energy, in MeV, when a proton is
converted into pure energy? The mass of a proton is 1.6726 X
10-27 Kg. Discovery
of
the
Electron
 J.J
Thompson
and
his
student
Robert
Millikan
are
credited
for
the
discovery
and
es9ma9on
of
the
charge
of
an
electron.
 Thompson
used
a
cathode
ray
tube
to
determine
the
charge
to
mass
ra9o
of
an
electron
and
then
Millikan
used
his
oil‐drop
experiment
to
determine
the
numerical
mass
of
the
droplet
and
its
charge
individuality.
JJ Thompson
The magnetic force acts as the centripetal force because it causes
the charges to bend. In addition the velocity selector uses the
balance of the electric and magnetic force to counter act one
another. This is how he calculated it:
Fmagnetic = Fcentripetal
2
mv e v
evB = ∴ =
r m Br
€
Felectric = Fmagnetic
E
eE = evB∴v = The call this the velocity selector equation
B
e E
= 2
m Br
€
Millikan then performed his oil drop experiment to
calculate the mass and charge of the electron.
qE = mdrop g ∴ q =
mdrop g
E
So Millikan could calculate the charge of the
electron from his experiment and then used
Thompson’s experiment to calculate the mass.
€
Planck’s
Quantum
Hypothesis;
Black
Body
Radia9on
−3
−34
*E = hf where h = 6.63×10 J • s
2.90 ×10 m•K
λp =
T
  As
an
object
heats
up
it
gives
off
radia9on.
At
lower
temperatures
this
radia9on
is
in
the
infra‐red
range
so
we
can
feel
the
heat
but
cannot
see
it.
As
it
gets
hoWer
the
radia9on
is
at
higher
frequencies
un9l
it
is
in
the
visible
range.
First
red,
then
orange,
blue,
and
then
white
hot
at
the
highest
frequency.
  He
also
proposed
that
this
experiment
showed
that
the
energy
of
these
waves
was
quan9zed,
it
was
mul9ples
of
some
fundamental
quan9ty,
and
related
it
to
the
frequency
of
the
radia9on.
What is the energy of a photon of red light with a wavelength
of 700 nm? Photon
Theory
of
Light
and
the
Photoelectric
Effect
  When
light
hits
metals
it
can
eject
electrons.
This
is
called
the
photoelectric
effect.
  Einstein,
building
on
Planck’s
idea
of
quan9zed
energy,
explained
the
photoelectric
effect
from
a
par9cle
theory
of
light
and
named
these
par9cles
of
light
‐
Photons.
  In
1913‐1914,
Millikan
performed
experiments
that
matched
Einstein’s
predic9on
of
light
as
a
par9cle
and
showed
that
the
wave
theory
of
light
predic9ons
were
incorrect
for
this
phenomenon.
E photon = hf
E kin = hf − Φ
= hf − hf o
Equa9ons
 Photoelectric
Effect
*KE max = hf − W o (φ )
  Stopping
Poten9al
  The
poten9al
to
stop
the
flow
of
electrons.
  Whatever
energy
that
the
electrons
would
ajer
being
ejected
is
equal
to
the
stopping
poten9al.
€
*KE max = eVo
Draw a graph that represents
the KE as a function of
frequency Draw a graph that represents
the KE as a function of the
intensity of incident light Wave
Verse
Par9cle
Predic9on
Wave
Theory
Photon
Theory
A)This
theory
would
predict
A)This
theory
predicted
that
that
as
the
light
intensity
as
the
intensity
increased
increased,
the
number
of
the
number
of
ejected
electrons
ejected
and
electrons
should
increase
their
KE
would
increase.
but
their
KE
should
not
be
B)The
frequency
of
the
light
effected.(E=hf)
should
not
affect
the
KE
B)
As
the
frequency
was
energy
of
the
electrons.
increased
the
maximum
KE
would
increase
and
that
there
should
be
some
minimum
threshold
frequency
to
eject
the
electrons.
Energy,
Mass,
and
Momentum
of
a
Photon
E hf h
*p = =
=
c
c λ
 Since
a
photon
travels
at
the
speed
of
light
it
is
a
rela9vis9c
par9cle.
If
then
Einstein’s
equa9ons
are
applied
then
the
photon
has
a
rest
mass
of
zero.
The
result
is
that
a
photon’s
momentum
is
directly
related
to
its
energy.
A photon has a momentum of p and a wavelength
the wavelength doubles, what will happen to the
momentum? €
λ.
If
Compton
Effect
h
λ′ = λ +
(1− cos φ )
moc
 In
addi9on
to
the
photoelectric
effect
another
experiment
done
by
A.H.
Compton,
1923,
also
supported
the
photon
theory
of
light.
€  He
scaWered
x‐rays
off
of
various
materials
and
found
that
the
resul9ng
x‐rays
had
a
slightly
lower
frequency
which
meant
some
energy
had
been
lost
in
the
collision.
He
explained
it
using
the
photon
theory
of
light.
Photon
Interac9ons;
Pair
Produc9on
 When
photons
pass
through
maWer
they
produce
maWer
and
an9maWer.
 When
the
photon
hits
the
maWer
it
will
produce
an
electron
and
a
positron.
This
is
an
example
of
energy
conver9ng
into
maWer.
 Positrons
usually
do
not
hang
around
in
nature
because
they
can
combine
with
electrons
and
annihilate
each
other
forming
photons
of
energy.
 This
principle
is
used
in
PET
scans.
h
h
*λ = =
p mv
Wave
Nature
of
MaWer
 In
1923,
Louis
de
Broglie,
proposed
that
if
light
has
a
wave/par9cle
duality
then
maWer
should
also.
 Ordinary
objects
have
wavelengths
that
are
very
small.
So
in
everyday
life
it
is
difficult
to
see
their
wave
nature.
However
electrons,
and
other
subatomic
par9cles,
move
fast
enough,
and
have
a
small
enough
mass,
that
their
wave
nature
can
be
detected
because
we
can
make
diffrac9on
gra9ngs
with
slits
on
the
order
of
their
wavelength
and
observe
diffrac9on
paWerns.
 C.J.
Davisson
and
L.H.
Germer
scaWered
electrons
(par9cles
of
maWer)
off
a
object
and
observed
a
regular
paWern
of
interference
peaks
that
Young’s
wave
theory
predicts.
 The
wavelength
matched
the
predic9on
of
de
Broglie’s
equa9on.
Which of the following experiments demonstrates the
wave nature of mater:
I.  Millikan’s Oil Drop Experiment
II.  Planck’s Black Body Radiation
III.  Davisson and Germer’s Electron Scattering
Experiment
A) I only
B) III only
C)I and II
D) I and III
Rutherford
 In
the
1897
electrons
were
discovered
and
by
1900
most
scien9sts
believed
that
maWer
was
made
of
atoms.
However,
the
structure
of
the
atoms
was
thought
to
be
a
posi9ve
pudding
like
material
with
nega9ve
charges
implanted
inside
of
it.
This
was
J.J.
Thomson’s
Theory
that
he
proposed
in1904.
 In
1911,
Ernest
Rutherford
did
his
famous
gold
foil
experiment
which
showed
that
the
atom
was
comprised
of
a
dense
core
surrounded
by
mostly
empty
space
and
surrounded
by
electrons
some
distance
away.
Rutherford’s gold foil experiment proved which of the
following postulates about the structure of the atom:
I) The atom has a core with electrons orbiting around
in discrete energy levels
II) The atom has a dense central positive core
III) The atom is mostly empty space
A) I only
B) III only
C)I and II
D) II and III
Atomic
Spectra:
Key
to
the
Structure
of
the
Atom
 When
you
place
a
low
density
gas,
rarefied,
in
a
glass
tube
and
pass
a
high
voltage
through
it
you
will
get
a
line
Emission
Spectra
which
is
characteris9c
of
the
element.
When
you
pass
a
light
source
through
the
gas
you
will
get
a
Absorp9on
Spectrum.
 The
fact
that
the
spectra
were
dis9nct
lines
and
not
con9nuous
lead
to
the
discovery
that
electrons
are
in
discrete
energy
levels
around
the
nucleus
or
“quan9zed”.
 Bohr’s
model
of
the
atom
accurately
explains
this
phenomenon.
These top three are Emission Spectra the bottom is an Absorption
Spectrum
−13.6eV
*E n =
2
n
Bohr
Model
  He
proposed
that
the
electrons
in
an
atom
must
be
in
only
certain
“allowed”
orbits
and
that
electrons
cannot
lose
energy
con9nuously
but
in
discrete
quantum
jumps.
While
remaining
in
these
states
they
did
not
give
off
radia9on
which
was
a
contradic9on
of
classical
ideas
because
accelera9ng
charges
should
give
off
EM
radia9on.
(
Mul9ple
of
Plank’s
constant)
  He
argued
that
electromagne9c
radia9on
was
emiWed
only
when
electrons
in
higher
energy
states
fell
to
lower
ones.
  He
named
the
lowest
energy
level
the
ground
state
and
all
levels
above
that
as
excited
states.
  The
energy
required
to
remove
the
electron
from
the
ground
state
is
called
the
binding
energy
or
ioniza9on
energy
Here’s an example:
A photon with an energy
of 3 eV hits this atom
and excites its outer
electron. What are the
possibly transitions that
the electron can do?
(Photons of what
energies can be
reemitted?)
Don’t forget:
1eV = 1.6 X 10-19 J
De
Broglie’s
Hypothesis
Applied
to
Atoms
 Although
the
idea
of
exact
Energy
levels
and
Bohr’s
equa9on
for
predic9ng
their
energy
falls
apart
ajer
Hydrogen
it
did
lead
to
the
next
great
step
in
our
understanding
of
the
atom,
quantum
mechanics.
 Although
Bohr
assumed
quan9zed
states
of
electrons
he
could
give
no
reason.
 Ten
years
later
de
Broglie
help
him
out
by
sta9ng
that
the
electrons
were
wave‐like
in
nature
and
were
actually
standing
waves.
Therefore
they
didn’t
have
to
follow
the
classical
rules
for
par9cles.
Quantum
Mechanics
of
Atoms
  Although
Bohr’s
theory
was
a
good
beginning
it
fell
apart
for
complex
molecules
and
other
fine
details.
  In
the
1920’s
Erwin
Schrodinger
and
Werner
Heisenberg
independently
formed
a
new
theory
that
resolved
the
problems
called
quantum
theory.
  Even
though
we
s9ll
use
classical
physics
to
describe
the
macroscopic
world,
rela9vity
to
describe
objects
moving
near
the
speed
of
the
light,
and
quantum
for
the
microscopic
world,
they
all
agree
and
we
use
whichever
is
the
most
easy
for
the
given
situa9on.
The
Wave
Func9on:
The
Double‐
Slit
Experiment
 If
you
pass
electrons
through
two
slits
that
is
on
the
order
of
magnitude
equal
to
their
wavelength
you
will
see
a
diffrac9on
paWern.
 However,
if
you
pass
them
through
one
slit
you
would
see
one
bright
band
behind
the
slit
as
if
they
are
par9cles.
 If
we
treat
electrons
as
waves
then
,
the
wave
Ψ
func9on
represents
the
amplitude
of
the
wave
and
Ψ2
represents
the
probability
of
finding
the
electron.
€
€
The
Heisenberg
Uncertainty
Principle
h
*(Δx)(Δp) ≥
= h = 1.055 ×10−34 J • s
2π
 According
to
quantum
there
is
a
natural
limit
to
the
accuracy
of
certain
measurements.
 It
is
result
of
the
wave‐par9cle
duality
and
the
unavoidable
interac9on
in
observing.
 The
act
of
observing
produces
an
uncertainty
in
the
posi9on
and
momentum
because
you
can
only
get
as
accurate
the
wavelength
of
light
being
used.
Quantum‐Mechanical
View
of
Atom
 Although
many
ideas
from
Bohr
are
s9ll
used,
Quantum
Theory
deepens
our
understanding
of
nature.
 Electrons
are
now
thought
of
as
maWer
waves
so
they
are
thought
of
as
clouds
of
maWer
spread
out.
The
most
sta9s9cally
likely
place
to
find
them
is
equivalent
to
Bohr’s
energy
levels.
Quantum
Numbers
 Principle
Quantum
Number(n)
 Values
1
to
infinity.
The
total
energy
depends
on
this
number.
 Orbital
Quantum
Number(l)
 This
is
related
to
the
angular
momentum
of
the
electron.
Values
range
from
0
to
n‐1
 Magne9c
Quantum
Number(ml)
 This
is
related
to
the
direc9on
of
the
angular
momentum.
Values
range
from
‐l
to
+l
 Spin
Quantum
Number
(ms)
 The
electron
can
have
two
intrinsic
states
that
split
its
energy.
Values
can
be
+
/‐
1/2
The
Pauli
Exclusion
Principle
 It
simply
states
that
no
two
electrons
can
occupy
the
same
quantum
state.
 This
principle
helps
us
describe
the
electron
configura9ons
of
more
complex
atoms
and
molecules.
Quantum concepts are critical in explaining all of the following
except:
A)  Rutherford’s Scattering experiments
B)  Bohr’s theory of the hydrogen atom
C)  Compton Scattering D)  Blackbody Radiation
E)  The photoelectric effect
Structure
and
Proper9es
of
Nucleus
 A
nucleus
is
the
dense
center
of
an
atom
and
contains
protons
and
neutrons.
 A
proton
has
a
mass
of
1.67262
X10‐27
kg
=
1.007276
u
and
a
posi9ve
charge
of
1.60
X10‐19
C.
 A
neutron
has
a
mass
off
1.67493
X10‐27
kg
=
1.008665
u
and
is
electrically
neutral.
 Collec9vely
they
are
referred
to
as
nucleons.
 The
number
of
protons
in
a
nucleus
is
called
the
atomic
number(Z)
and
gives
an
atom
its
iden9ty.
Memorize this conversion
−27
1u = 1.6605 ×10 Kg = 931.5Mev /c
€
2
 The
number
of
protons
and
neutrons
is
referred
to
as
the
atomic
mass
number(A)
or
simply
mass
number.
 The
neutrons
is
the
difference
between
the
atomic
and
mass
number.
 Atoms
can
have
numerous
Isotopes.
Isotopes
are
atoms
of
the
same
element
with
different
numbers
of
neutrons.
The
rela9ve
amount
of
each
isotope
is
called
the
natural
abundance.
 Masses
are
also
measure
in
unified
atomic
mass
units(u).
An element has an atomic number Z of 1. Although many
of the atoms have zero number of neutrons, N, some have
one or two neutrons. These different atoms are know as:
A) Ions
B) Nucleons C) Isotopes
D) Gluons Binding
Energy
 The
total
mass
of
a
nucleus
is
always
lees
than
the
sum
of
the
protons
and
neutrons
individually.
 The
mass
of
the
protons
and
neutrons
in
a
Helium
atom
is
4.0332980
while
the
measured
mass
is
4.002603
u.
The
difference
is
.030377
u
which
when
you
mul9ple
by
931.5
MeV
that
equals
28.30
MeV
of
binding
energy.
 The
binding
energy
represent
the
energy
needed
to
break
it
into
its
component
parts.
 To
find
the
the
binding
energy
per
nucleon
you
simply
divide
by
the
number
of
nucleons
(A)
The deuteron mass md is related to the neutron mass mn and
the proton mass by mp by which of the following
expressions? A)  md= mn-mp
B)  md= mn+mp
C)  md=2( mn-mp)
D)  md= mn+mp-(mass equivalent to deuteron binding energy)
E)  md= mn+mp+(mass equivalent to deuteron binding energy)
Radioac9vity
 Stable
nuclei
tend
to
have
equal
numbers
of
protons
and
neutrons.(Up
to
element
40‐
Zirconium)
 Ajer
element
82(Lead)
there
are
no
completely
stable
nuclei.
At
this
point
the
nucleus
is
too
big
for
the
strong
force
to
hold
together
the
atom
and
the
repulsive
EM
force
rips
the
nucleus
apart.
 When
this
happens
in
nature
it
is
called
“Natural
Radioac9vity”
when
man‐made
it
is
“Ar9ficial
Radioac9vity”.
The higher the atomic number the more neutrons are
needed to stablize the atom.
Radioac9ve
Decay
 There
are
three
kinds
of
radioac9ve
decay:
Alpha,
Beta,
Gamma.
In
the
process
one
element
turns
into
another
element
and
this
is
called
transmuta9on.
The
original
atom
is
called
the
parent
and
the
new
one
is
called
the
daughter.
 Alpha
is
the
weakest
of
the
three.
It
can
be
stopped
by
a
piece
of
paper
and
is
actually
a
ionized
Helium
atom.
4
2
+2
He = α
 Beta
is
the
second
strongest
and
could
be
stopped
by
a
block
of
wood.
It
is
simply
an
0
−
0
+
e
=
β
or
e
=
β
electron
(positron).
−1
+1
 Gamma
is
the
strongest
and
takes
12
in
of
lead
or
10
j
of
concrete
to
block.
γ
€
Here are some examples:
Alpha
226
88
222
86
Ra→ Rn+ He
Beta
14
6
4
2
14
7
−
C→ N + e + ν
19
10
19
9
+
Ne→ F + e + ν
Gamma
14 ∗
6
14
6
C → C+γ
Example:
A neutron collides with
32
16
S and
produces 1733Cl and another
particle. The
€ other particle is
A) 
€ Proton
B)  Alpha Particle
C)  Beta Particle D)  Neutron
E)  Deuteron
Half‐Life
and
Rate
of
Decay
.693
*T1 = where τ is the time constant
2
τ
*N = N oe
€
t
τ
If they ask for the activity you just divide this
equation by time
 Radioac9ve
elements
decay
at
a
constant
rate.
 Ojen
instead
of
speaking
of
its
decay
constant
we
speak
instead
of
it’s
half
life,
or
the
9me
it
take
for
1/2
of
the
sample
to
decay.
Radioac9ve
Da9ng
 Any
living
organism
contains
a
constant
ra9o
of
Carbon‐14
and
to
Carbon‐12
un9l
it
dies.
Carbon
‐14
has
a
half
life
of
5730
yr.
So
by
looking
at
ancients
remains
of
trees,
poWery,
and
people
the
ra9o
of
C‐14
to
C‐12
can
tell
us
its
age.
Good
up
to
60,000
yrs.
 So
obviously
when
talking
about
geological
9me
this
would
not
be
useful.
However,
Uranium‐238
has
a
half‐life
of
4.5
X109
yrs
so
this
is
used
to
date
ancient
rocks.
  For
example:
How
old
is
a
wooly
mammoth
fossil
that
that
had
100.0
grams
of
C‐14
when
alive
and
it’s
fossil
has
12.5
grams
lej
when
you
find
it?
Nuclear
Reac9ons
and
Transmuta9on
 A
nuclear
reac9on
is
said
to
be
different
from
radioac9vity
because
the
transmuta9on
occurs
when
a
nucleus
is
bombarded
by
another
par9cle
or
photon
of
energy.
 In
the
1930’s,
Enrico
Fermi
and
his
colleagues,
bombarded
atoms
with
neutrons
and
produced
“transuranic”
elements,
elements
heavier
than
uranium.
Nuclear
Fission
1
0
€
235
92
141
56
93
36
1
0
n+ U→ Ba+ Kr +3 n
 In
1938
OWo
Hahn
and
Lise
Meitner
discovered
that
when
uranium
absorbed
slow
neutrons
it
could
be
split
apart.
They
named
this
Nuclear
Fission.
During
this
nuclear
reac9on
energy
was
produced
and
this
was
the
basis
for
the
atomic
bomb
(uncontrolled
chain
reac9on)
and
nuclear
power
plants(controlled
reac9on).
 In
order
to
keep
a
chain
reac9on
going
you
need
a
certain
amount
of
uranium
to
allow
a
chain
reac9on.
This
is
called
the
cri9cal
mass.
Nuclear
Fusion
1
1
4
2
−
4 H→ He + 2e + 2ν + 2γ
 The
process
of
building
up
nuclei
by
bringing
together
protons
and
neutrons
together
into
larger
nuclei
is
called
Fusion.
 This
is
the
process
happening
in
stars
and
in
the
process
mass
is
converted
into
energy
according
to
E=mc2.
€
1
0
10
5
7
3
4
2
n+ B→ Li+ He
The above equation is an example of
I. Nuclear Bombardment
II. Nuclear Fission
III. Nuclear Fusion
IV. Alpha Decay
A) I only
B) II only
C) I &III
D) I&IV
Measurement
of
Radia9on
Dosimetry
ΔN
.693
= λN =
N
Δt
T1/ 2
 The
strength
of
a
source
can
be
specified
at
a
given
9me
by
sta9ng
the
source
ac9vity,
or
the
disintegra9ons
per
second.
€
 1
Curie(Ci)
=
3.70
X
1010
dis/sec
 1
becquerel(Bq)
=
1
dis/sec
 Another
measurement
is
the
amount
of
radia9on
absorbed.
 1
Rad
=
1.00
X
10‐2
J/Kg
 1
Gray(Gy)
=
100
Rad