“If t
he w
hole
uni
vers
e ha
s no
mea
ning
, we
shou
ld n
ever
hav
e fo
und
out t
hat i
t has
no
mea
ning
: jus
t as,
if th
ere
wer
e no
ligh
t in
the
univ
erse
and
ther
efor
e no
cre
atur
es
with
eye
s, w
e sh
ould
nev
er k
now
it w
as
dark
. Dar
k w
ould
be
with
out m
eani
ng.”
C.S
. Lew
is
The
Hub
ble
Ultr
a D
eep
Fie
ld
Wha
t We
Will
Lea
rn T
oday
•W
hat a
re y
ou s
eein
g rig
ht n
ow?
•W
hat a
re th
e ba
sic
prop
ertie
s of
ligh
t?•
Wha
t is
the
Ele
ctro
mag
netic
S
pect
rum
?•
Wha
t are
the
basi
c bu
ildin
g bl
ocks
of
mat
ter?
•H
ow d
oes
light
inte
ract
with
mat
ter?
Ligh
t
•E
very
thin
g w
e se
e is
ligh
t!•
We
only
see
a ti
ny w
indo
w o
f all
the
light
ther
e is
!•
All
of a
stro
nom
y is
the
stud
y of
ligh
t!•
So,
let’s
und
erst
and
light
, mat
ter,
and
ho
w t
he tw
o in
tera
ct!
Wha
t We
See
Aro
und
Us
•Li
ght e
mitt
edfr
om th
e S
un o
r lig
ht b
ulb
•T
rans
mitt
edlig
ht•
Ref
lect
edlig
ht•
Col
ors
of o
bjec
ts (
part
ly a
bsor
bed
)
Fig
5.3
The
Nat
ure
of L
ight
•Li
ght i
s m
ade
up o
f tin
y pa
rtic
les
–P
hoto
ns
•E
ach
phot
on d
emon
stra
tes
a w
ave-
like
beha
vior
•T
hus,
ligh
t is
both
a p
artic
le a
nd a
w
ave
at th
e sa
me
time!
You
ng’s
Dou
ble
Slit
Exp
erim
ent
•P
roof
of t
he w
ave
natu
re o
f lig
ht
Wav
e P
rope
rtie
s of
Lig
ht
•W
avel
engt
h (λ
)•
Fre
quen
cy (ν)
•S
peed
(c)
–co
nsta
nt fo
r al
l fla
vors
of l
ight
•H
ighe
r w
avel
engt
h im
plie
s lo
wer
fre
quen
cy–
And
vic
e-ve
rsa
•E
nerg
y ca
rrie
d by
ligh
t (ra
diat
ive
ener
gy, E
)
•H
ighe
r fr
eque
ncy
impl
ies
high
er e
nerg
y–
Als
o im
plie
s sm
alle
r w
avel
engt
h
“Fla
vors
” of
ligh
t
λυ=
c
υhE
=h
= P
lanc
k’s
cons
tantF
ig 5
.5 b
The
Ele
ctro
mag
netic
Spe
ctru
mG
X
U
V
I
R
V I
B G
Y O
R40
0 –
700
nm
Fig
5.7
The
Bui
ldin
g B
lock
s of
Mat
ter
•S
mal
lest
to la
rges
t–
Qua
rks
& L
epto
ns–
Nuc
leus
(P
roto
ns, N
eutr
ons)
& S
hells
(E
lect
rons
)–
Ato
ms
–M
olec
ules
Fig
5.8
Ato
ms
•In
cred
ibly
sm
all
–M
illio
ns c
an fi
t in
one
perio
d at
the
end
of a
se
nten
ce in
a ty
pica
l boo
k–
Num
ber
of a
tom
s in
a d
rop
of w
ater
exc
eeds
th
e nu
mbe
r of
sta
rs in
the
Uni
vers
e!
•A
tom
s ar
e m
ostly
em
pty
–If
nucl
eus
is th
e si
ze o
f you
r fis
t, el
ectr
on
clou
ds a
re m
any
mile
s aw
ay!
•N
ucle
us c
onta
ins
mos
t of t
he m
ass
•E
lect
rons
inha
bit s
peci
fic s
hells
bas
ed o
n en
ergy
leve
ls
Pha
ses
of M
atte
r
•Lo
osel
y bo
und
to ti
ghtly
bou
nd–
Hot
test
to c
oole
st–
Ful
ly io
nize
d pl
asm
a (s
tella
r co
res)
–P
lasm
a (s
tella
r in
terio
rs)
–M
olec
ular
dis
asso
ciat
ion
(Ear
th c
ore)
–M
olec
ular
pha
ses
(Ear
th s
urfa
ce)
•G
as p
hase
•
Liqu
id p
hase
•S
olid
pha
se
Fig
5.1
0
Che
mic
al E
lem
ents
•D
efin
ed b
ased
on
num
ber
of p
roto
ns in
the
nucl
eus
(ato
mic
num
ber)
•In
gen
eral
, num
ber
of e
lect
rons
and
neu
tron
s eq
ual t
he n
umbe
r of
pro
tons
(ex
cept
ions
exi
st)
–D
iffer
ent n
umbe
r of
ele
ctro
ns: i
ons
–D
iffer
ent n
umbe
r of
neu
tron
s: is
otop
es
•M
olec
ules
are
com
bina
tions
of e
lem
ents
–H
20 =
one
mol
ecul
e of
wat
er•
2 at
oms
of H
, plu
s
•1
atom
of O
Impo
rtan
t Ele
men
ts in
Ast
rono
my
•H
ydro
gen
(H, n
= 1
)–
Sim
ples
t ele
men
t: 1
prot
on +
1 e
lect
ron
–M
ost a
bund
ant e
lem
ent i
n th
e un
iver
se (
74%
)–
Ove
r 90
% o
f the
Sun
’s m
ass
•H
eliu
m (
He,
n =
2)
–2
prot
ons,
2 n
eutr
ons,
2 e
lect
rons
–24
% o
f the
uni
vers
e, 9
% o
f the
Sun
•C
arbo
n (C
, n =
6)
–0.
05%
of t
he u
nive
rse,
0.0
3% o
f the
Sun
–B
asis
of a
ll lif
e fo
rms
on E
arth
•N
itrog
en (
N, n
= 7
)–
Prin
cipa
l com
pone
nt o
f Ear
th’s
atm
osph
ere
•O
xyge
n (O
, n =
8)
–0.
1% o
f the
uni
vers
e, 0
.08%
of t
he S
un
•Ir
on (
Fe,
n =
26)
–D
ense
st n
ucle
us, r
easo
n fo
r S
uper
nova
e
Key
Mol
ecul
esH
2
H2O
CH
4
NH
3
Inte
ract
ion
of L
ight
with
Mat
ter
•A
bsor
ptio
n lin
e–
Pho
ton
abso
rbed
by
elec
tron
to ju
mp
to h
ighe
r en
ergy
leve
l
•E
mis
sion
line
–P
hoto
n em
itted
by
elec
tron
to ju
mp
back
to lo
wer
ene
rgy
leve
l
•O
nly
spec
ific
ener
gy le
vels
of p
hoto
ns a
bsor
bed
or
emitt
ed–
i.e. o
nly
spec
ific
wav
elen
gths
or
colo
rs
n= 1
(G
roun
d st
ate)
E =
-13
.6 e
V
n= 2
, E =
-3.
4 eV
n= 3
, E =
-1.
5 eV
n= 4
, E =
-0.
85 e
Vn=
5, E
= -
0.5
eV
Recommended
