Feb
11,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
Ast
rono
my
210
Sect
ion
1–M
WF
150
0-15
5013
4 A
stro
nom
y B
uild
ing
Thi
s C
lass
(L
ectu
re 1
1):
Spec
tros
copy
Nex
t Cla
ss:
Mat
ter
and
Lig
ht
Mus
ic: S
pace
Dog
–T
oriA
mos
Pla
neta
rium
Obs
ervi
ng
Star
dial
Obs
ervi
ng
Exa
m #
1 ne
xt w
eek
Feb
11,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
Out
line
•L
ight
•Sp
ectr
osco
py
•T
he a
tom
Feb
11,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
The
Spe
ctru
m
Ab
sorp
tio
n
The
“sp
ectr
um”
of a
ligh
t sou
rce
also
ref
ers
to th
e fr
actio
nal
cont
ribu
tion
of a
ll of
the
diff
eren
t wav
elen
gths
to it
s to
tal l
ight
ou
tput
. It i
s th
e Fl
ux d
istr
ibut
ion
vsλ.
wav
elen
gth
flux
Em
issi
on
wav
elen
gth
flux
Feb
11,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
Spec
trum
Lin
es
•Fr
aunh
ofer
disc
over
ed th
at S
un’s
sp
ectr
um c
onta
ined
nar
row
gap
s (a
bsor
ptio
n lin
es)
whe
n vi
ewed
at
high
res
olut
ion
(181
4)
Pris
m s
pect
rogr
aph
Feb
11,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
Wha
t Col
or is
Sun
light
?
http
://a
ntw
rp.g
sfc.
nasa
.gov
/apo
d/ap
0008
15.h
tml
Feb
11,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
Spec
trum
Lin
es
•W
hen
astr
onom
ers
look
ed a
t the
sp
ectr
a of
the
Sun
and
star
s,
they
saw
gap
s•
Not
a p
erfe
ct
smoo
th
spec
trum
!•
Cal
led
dark
sp
ectr
um li
nes
Feb
11,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
In th
e L
abor
ator
y
•B
righ
t spe
ctru
m
lines
wer
e pr
oduc
ed a
nd
stud
ied
in th
e la
bora
tory
in
the
mid
-180
0s
•D
isco
vere
d th
at b
urni
ng d
iffe
rent
che
mic
al
elem
ents
pro
duce
d di
ffer
ent p
atte
rns
of
lines
Feb
11,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
Spec
trum
Lin
es =
Fin
gerp
rint
s
The
pat
tern
of
spec
trum
line
s pr
oduc
ed b
y a
gas
depe
nds
on it
s ch
emic
al c
ompo
sitio
n
http
://w
ww
.ast
ro.w
ashi
ngto
n.ed
u/as
tro1
01v
Or
a ba
rcod
e!
Feb
11,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
Kir
chof
f's
Law
s
•In
185
9, G
usta
v K
irch
hoff
disc
over
ed th
e co
nditi
ons
unde
r w
hich
thre
e ba
sic
type
s of
sp
ectr
a ar
e fo
rmed
:–
A h
ot, d
ense
obj
ect p
rodu
ces
a co
ntin
uous
sp
ectr
um
–A
hot
low
-den
sity
gas
pro
duce
s an
em
issi
on-
line
spec
trum
–A
con
tinuo
us s
pect
rum
sou
rce
view
ed th
roug
h a
cool
er g
as p
rodu
ces
an a
bsor
ptio
n-lin
e sp
ectr
um
Feb
11,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
Kir
chof
f's
Law
s
Feb
11,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
Kir
chof
f's
Law
s Not
e th
at th
e em
issi
on
lines
hav
e sa
me
wav
elen
gth
as m
issi
ng
flux
.
Feb
11,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
Wha
t Col
or is
Sun
light
?
Sun
is a
hot
, de
nse
obje
ct
So, t
here
mus
t be
a c
oole
r, le
ss
dens
e so
lar
atm
osph
ere
surr
ound
ing
it.
http
://a
ntw
rp.g
sfc.
nasa
.gov
/apo
d/ap
0008
15.h
tml
Feb
11,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
How
Do
Spec
trum
Lin
es F
orm
?
To
answ
er th
is q
uest
ion,
we
need
to d
elve
in
to th
e st
ruct
ure
of m
atte
r its
elf…
Feb
11,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
Stat
es o
f M
atte
r
•So
lid
–D
efin
ite s
hape
an
d vo
lum
e
•L
iqui
d–
Def
inite
vol
ume,
fl
exib
le s
hape
•G
as –Fl
exib
le
shap
e an
dvo
lum
e
Feb
11,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
A G
lass
of
Wat
erA
Gla
ss o
f W
ater
10 cm
1 nm
= 1
0-9m
0.1
nm
Wat
er m
olec
ules
Oxy
gen
atom
1 fm
= 1
0-15
mO
xyge
n nu
cleu
s
Feb
11,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
Par
ts o
f an
Ato
m
Ato
ms
are
mad
e of
ele
ctro
ns,
prot
ons,
and
neu
tron
s
Electrons
Neg
ativ
ely
char
ged
(cha
rge
-1)
Ligh
twei
ght
(mas
s 9.
110
x 10
-28
g)
Protons
Posi
tivel
y ch
arge
d (c
harg
e +
1)18
32 t
imes
as
mas
sive
as
an e
lect
ron
(mas
s 1.
673
x 10
-24
g)
Neutrons
No
elec
tric
cha
rge
A lit
tle m
ore
mas
sive
tha
n a
prot
on (
mas
s 1.
675
x 10
-24
g)
Feb
11,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
Ato
ms
and
Ele
men
ts
•A
ll m
atte
r is
mad
e of
ele
men
ts–
92 n
atur
al a
nd 2
3+ a
rtif
icia
l–
Hyd
roge
n, C
arbo
n, O
xyge
n, I
ron,
Ura
nium
, etc
.–
Eac
h el
emen
t is
com
pose
d of
a d
iffe
rent
kin
d of
ato
m•
The
num
ber
of p
roto
ns (
or Z
) in
an
atom
de
term
ines
the
type
of
elem
ent
–H
ydro
gen
has
1 pr
oton
(Z
=1)
, oxy
gen
has
8 pr
oton
s (Z
=8)
, etc
.•
Neu
tron
s ar
e “p
acki
ng m
ater
ial”
.•
Ato
ms
inte
ract
via
ele
ctro
ns–
Shar
ed a
mon
g at
oms
to m
ake
mol
ecul
es–
Ato
ms
mis
sing
or
with
ext
ra e
lect
rons
are
cal
led
ions
Feb
11,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
Per
iodi
c T
able
Feb
11,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
Isot
opes
•Sa
me
elem
ent (
sam
e #
p) c
an h
ave
diff
eren
t #
neut
rons
.
⇒is
otop
es
•Fo
r ex
ampl
e, m
ost H
is 1 H
= 1
p, 0
n
•bu
t ∼10
-4of
H is
deu
teri
um 2 H
= 1
p, 1
n
•A
bout
10
kg o
f yo
ur b
ody
is 1 H
, and
1g
is
deut
eriu
m
•O
r m
ost U
is 2
38U
= 9
2p, 1
46n
http
://w
ww
.ste
elbr
igad
e.co
m/S
Bpr
omot
ions
.htm
l
Feb
11,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
Bal
mer
•E
mpi
rica
lly f
ound
wav
elen
gths
of
H e
mis
sion
lin
es
•W
hat d
oes
this
tell
us?
nmnn
n
65
64
9
910
65.3
3n
for
3in
tege
r
for
410
65.3
7
2
27
=−
×=
=
≥−
×=
−−
λλ
Feb
11,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
Prin
ce L
ouis
-Vic
tor
de B
rogl
ie
•N
ot o
nly
does
ligh
t be
have
s lik
e pa
rtic
le &
w
ave,
but
so
does
mat
ter!
⇒m
atte
r w
aves
exi
st!
•T
hen
wha
t is
the
wav
elen
gth?
mvh
ph
ph
Ehc
hE
cc
==
==
==
λ
νλ
:sa
me
th
ebe
mus
t m
atte
r Fo
r
/
:ph
oton
sFo
r
Feb
11,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
Boh
r’s
Ato
m
•B
ohr
mod
el o
f th
e at
om•
Qua
ntum
str
uctu
re: e
-or
bits
are
mat
ter
wav
es•
Sem
icla
ssic
al: m
ixes
New
toni
an &
qua
ntum
idea
s•
de B
rogl
iew
aves
⇒st
andi
ng w
aves
in a
tom
•e-
orbi
ts a
re c
ircu
lar
•O
nly
cert
ain
radi
i, sp
eeds
allo
wed
—qu
antiz
ed
stat
es ⇒
only
cer
tain
allo
wed
ene
rgie
s•
Dur
ing
e-tr
ansi
tions
bet
wee
n st
ates
, pho
ton
emitt
ed•
So, p
hoto
n en
ergi
es q
uant
ized
⇒sp
ectr
al li
nes
Feb
11,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
Ato
mic
Str
uctu
re•
Ele
ctro
ns o
rbit
the
nucl
eus
of e
ach
atom
•T
he n
ucle
us c
onsi
sts
of p
roto
ns a
nd n
eutr
ons
•N
umbe
r of
pro
tons
= n
umbe
r of
ele
ctro
ns
(t
otal
cha
rge=
0)•
The
ele
ctro
ns c
an
only
hav
e sp
ecia
l or
bits
cal
led
ener
gy le
vels
•T
he lo
wes
t ene
rgy
leve
l is
the
grou
nd s
tate
Gro
und
stat
e
Onl
y 4
leve
ls s
how
n
Hyd
roge
n at
om
Feb
11,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
Exp
lain
ing v
mhn
nr
e
==
λπ2
Ele
ctro
n be
com
es a
sta
ndin
g w
ave.
Sin
ce th
e or
bit
is d
efin
ed, o
nly
cert
ain
valu
es a
llow
ed, s
uch
that
Feb
11,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
Orb
it
•So
, if
the
elec
tron
is in
an
orbi
t, w
hat i
s th
e fo
rce?
•C
oulo
mb
forc
e pr
ovid
es c
entr
ipet
al a
ccel
erat
ion.
Lik
e gr
avity
, but
dif
fere
nt.
Feb
11,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
Orb
it
•So
, if
the
elec
tron
is in
an
orbi
t, w
hat i
s th
e fo
rce?
•C
oulo
mb
forc
e pr
ovid
es c
entr
ipet
al a
ccel
erat
ion.
Lik
e gr
avity
, but
dif
fere
nt.
)0
42
2
2 :
units
ch
arge
(c
gsπ
εSIe
SIke
cgs
e=
=
Feb
11,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
Orb
it
•So
, if
the
elec
tron
is in
an
orbi
t, w
hat i
s th
e fo
rce?
•C
oulo
mb
forc
e pr
ovid
es c
entr
ipet
al a
ccel
erat
ion.
Lik
e gr
avity
, but
dif
fere
nt.
Feb
11,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
How
Do
Spec
trum
Lin
es F
orm
?
•Sp
ectr
um li
nes
corr
espo
nd to
ele
ctro
n tr
ansi
tions
be
twee
n en
ergy
leve
ls in
an
atom
•A
bsor
ptio
n:li
ght
ener
gy a
bsor
bed
by
atom
, ele
ctro
n ju
mps
to
a h
ighe
r en
ergy
leve
l
•E
mis
sion
:el
ectr
on
drop
s do
wn
to lo
wer
en
ergy
leve
l; re
leas
es
ener
gy a
s lig
ht
Feb
11,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
Cha
nges
in L
evel
s
•Fo
r a
tran
sitio
n, th
e ph
oton
em
itted
or
abso
rbed
is f
rom
the
diff
eren
ce in
leve
l
•If
ele
ctro
n go
es f
rom
n a⇒
n bw
ith n
a>
nbth
en
phot
on e
nerg
y w
ill b
e
22
22
2
4
22
2
4 2
11
2
ba
ba
e
ba
e
nn
nn
nn
me
nn
me
EE
Eb
a
−=
−=
−=
hh
γ
Feb
11,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
Lam
bda,
Lam
bda,
Lam
bda 1
74
3
101.1
4
defi
neca
n
−×
==
=m
me
cR
Ehc
ehπ
λγ
γ
Ryd
berg
cons
tant
22
22
1
ba
ba
nn
nn
R−
=γλ
With
nb=
2, w
e ob
tain
the
Bal
mer
resu
lt!
Feb
11,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
Seri
es
new
uni
t: 1
eV=
1.6
02 x
10-1
9J
Or
the
amou
nt o
f en
ergy
gai
ned
by
an e
lect
ron
afte
r go
ing
thro
ugh
a po
tent
ial o
f 1
Vol
t.
n b=
1 ⇒
Lym
an s
erie
s
nb=
2 ⇒
Bal
mer
seri
es
nb=
3 ⇒
Pasc
hen
seri
es
Feb
11,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
How
Do
Spec
trum
Lin
es F
orm
?•
Spec
tral
line
s co
rres
pond
to e
lect
ron
tran
sitio
ns b
etw
een
ener
gy le
vels
in a
n at
om•
Exc
itat
ion:
elec
tron
jum
ps to
a h
ighe
r en
ergy
leve
l
(E
b<
Ea)
–C
ollis
ion
–γ
abso
rptio
n
•E
mis
sion
:el
ectr
on d
rops
do
wn
to lo
wer
en
ergy
leve
l; re
leas
es e
nerg
y (E
b>
Ea)
–C
ollis
ion
–Sp
onta
neou
s
Feb
11,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
Ato
m C
ollis
ions
•E
lect
rons
get
kno
cked
-up
to h
ighe
r en
ergy
leve
ls b
y co
llisi
ons
Feb
11,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
Cre
atio
n of
Abs
orpt
ion
and
Em
issi
on L
ine
Spec
tra
Feb
11,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
Ioni
ze th
e A
tom
•A
ll E
nar
e bo
und
stat
es, E
< 0
neg
ativ
e en
ergi
es
•A
lso
ther
e ar
e un
boun
d st
ates
, E >
0, w
here
the
e-is
fre
ed ⇒
ioni
zed!
•W
hat i
s m
in E
to io
nize
H f
rom
gro
und
stat
e (n
= 1
)? eVR
chnR
chE
Eio
nize
6.13
21
−=
= − −
=−
=
Feb
11,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
Vis
ible
-ligh
t pic
ture
of a
cat
(Tem
pera
ture
312
K)
Bla
ckbo
dy R
adia
tion
•L
ight
that
obj
ects
em
it be
caus
e of
thei
r te
mpe
ratu
re is
cal
led
blac
kbod
y ra
diat
ion
•B
lack
body
rad
iatio
n is
com
pose
d of
a c
ontin
uous
spe
ctru
m o
f w
avel
engt
hs•
The
hot
ter
an o
bjec
t get
s, th
e m
ore
inte
nse
and
shor
ter
wav
elen
gth
(blu
e-er
) its
bla
ckbo
dy r
adia
tion
beco
mes
Infr
ared
pic
ture
of a
cat
(Tem
pera
ture
312
K)
Vis
ible
-ligh
t pic
ture
of a
sto
ve e
lem
ent
(Tem
pera
ture
~ 4
00 K
)
Feb
11,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
Glo
win
g B
odie
s
•So
, eve
ryth
ing
we
know
is in
fac
t giv
ing
off
light
–as
long
as
it ha
s a
tem
pera
ture
, it i
s gl
owin
g.•
The
hig
her
the
tem
pera
ture
the
shor
ter
the
wav
elen
gth
it gl
ows
in–
com
pare
the
pers
on o
n th
e ri
ght (
in th
e ne
ar in
frar
ed)
and
a lig
ht b
ulb
(in
the
visi
ble)
.
http
://w
ww
.x20
.org
/ther
mal
/the
rmal
_wea
pon_
sigh
t_T
IWS3
20.h
tm
Feb
11,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
Def
ine
Bla
ckbo
dy
•A
per
fect
abs
orbe
r of
ligh
t•
It r
e-em
its r
adia
tion
acco
rdin
g to
its
tem
pera
ture
•T
here
fore
, “bl
ackb
ody
radi
atio
n" =
ther
mal
ra
diat
ion
•U
sual
ly, m
ost f
amili
ar o
bjec
ts a
re w
ell
appr
oxim
ated
as
blac
kbod
y ra
diat
ors
•A
cle
ar e
xcep
tion
is a
lase
r po
inte
r.–
Why
?
•T
he s
pect
rum
of
this
idea
l, on
ly
depe
nds
on it
s te
mpe
ratu
re!
Feb
11,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
The
Spe
ctru
m o
f B
lack
body
Rad
iatio
n
•Fl
ux is
> 0
for
all
λ•
The
hig
her
the
tem
pera
ture
, the
hig
her
the
flux
for
all
λ(c
urve
s do
not
inte
rsec
t!)
•Fo
r hi
gher
tem
pera
ture
the
max
imum
oc
curs
at s
hort
er w
avel
engt
hs.
Feb
11,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
The
Spe
ctru
m o
f B
lack
body
Rad
iatio
n
•Fl
ux is
> 0
for
all
λ•
The
hig
her
the
tem
pera
ture
, the
hig
her
the
flux
for
all
λ(c
urve
s do
not
inte
rsec
t!)
•Fo
r hi
gher
tem
pera
ture
the
max
imum
oc
curs
at s
hort
er w
avel
engt
hs.
T
mK
10
9.2Law
sW
ein'
3
max
−×
=λ
Feb
11,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
Thi
nk-P
air-
Shar
e
Whi
ch s
tar
is h
otte
r?–
Veg
a (b
lue)
–C
apel
la(y
ello
w)
–A
ntar
es(r
ed)
Feb
11,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
Red
Hot
?
•A
ctua
lly R
ed h
ot is
not
too
hot.
•B
lue
hot i
s ho
t.•
Whi
te h
ot is
eve
n ho
tter.
Feb
11,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
The
Spe
ctru
m o
f B
lack
body
Rad
iatio
n
The
Sun
’s s
pect
rum
look
s al
mos
t lik
e a
5800
K
blac
kbod
y.
Thi
s is
a v
ery
pow
erfu
l too
l!
We
can
find
the
tem
pera
ture
by
the
spec
trum
.
Col
or ⇔
Tem
pera
ture
!
K 58
00m
1050
0
K m
102.
9T
So,
nm 50
0
at
is
max
imum
sSu
n'
9
3-
=××
≈
≅
−
Feb
11,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
Bla
ckbo
dy F
lux-
ed
•T
he to
tal f
lux
from
a
blac
kbod
y is
add
ing
up th
e fl
ux in
the
spec
trum
.
•D
o yo
u th
ink
it de
pend
s on
tem
pera
ture
?
•St
rong
ly d
epen
dent
on
tem
pera
ture
.
–F
= σ
T4
ener
gy p
er p
erun
it ar
ea p
er u
nit t
ime
Feb
11,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
Bla
ckbo
dy F
lux-
ed
•T
he to
tal f
lux
from
a
blac
kbod
y is
add
ing
up th
e fl
ux in
the
spec
trum
.
•D
o yo
u th
ink
it de
pend
s on
tem
pera
ture
?
•St
rong
ly d
epen
dent
on
tem
pera
ture
.
–F
= σ
T4
ener
gy p
er p
erun
it ar
ea p
er u
nit t
ime
Bol
tzm
ann
-St
efan
m
W
1067.5
42-
8−
−×
=K
σ
Feb
11,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
Step
han-
Bol
tzm
ann
Law
•E
xam
ple
1: I
f a
star
was
the
sam
e si
ze a
s th
e Su
n, b
ut w
as
twic
e as
hot
, it w
ould
be
16 t
imes
as b
righ
t.
•E
xam
ple
2: T
he to
tal r
ate
of e
nerg
y em
issi
on f
rom
Sun
=
tota
l sol
ar p
ower
out
put =
sol
ar lu
min
osity
27
28
26
103.6
)10
0.7(4
1085.3
mW
mW×
=××
=π
WL
2610
85.3×
=G
KF
T58
0041
=
=
σ
