“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