370

DOC. 34

EMISSION

&

ABSORPTION

OF

RADIATION

Published

in

Deutsche

Physikalische Gesellschaft. Verhandlungen

18

(1916):

318-323.

Re-

ceived

17 July

1916, published

30

July

1916.

[1]See

Planck

1900b.

[2]See

Planck

1900a, in particular

the discussion

leading to eq.

(34).

[3]Einstein refers

to

Max Planck's calculation of the basic units of

charge

and

mass:

the

electron's

charge and

the

mass

of the

hydrogen atom

(see

especially

Planck

1901b).

[4]See

in particular

Einstein 1907a

(Vol. 2,

Doc.

38);

see

also the reviews of the work

on

specific

heats

by

Einstein and Walther Nernst

at

the first

Solvay Congress,

Einstein 1914a

(Vol. 3,

Doc.

26),

and Nernst

1914 (or

the French

version,

Nernst

1912).

[5]See

Einstein

1909b,

1909c

(Vol. 2,

Docs.

56 and 60)

for Einstein's

analysis

of the incom-

patibility

of the

quantum hypothesis

and classical

electromagnetism.

[6]For

Planck's

attempts to

revise his

theory,

see

his

Solvay report,

Planck 1914a

(or

the

French

version,

Planck

1912b),

and Planck

1914c.

[7]See

Bohr

1913.

[8]Einstein

expressed

his enthusiasm for the work

presented

in

this

paper

more

strongly

in

a

letter

to

Michele Besso of

11

August 1916,

when he

wrote:

"A

splendid

idea

on

the

absorp-

tion and

emission

of

radiation has dawned

on

me"

("Es

ist mir ein

prächtiges

Licht über die

Absorption

und Emission der

Strahlung

aufgegangen").

He

called his derivation of Planck's

law

"amazingly simple" ("verblüffend einfach"),

characterizing

it

as

"the derivation"

("die

Ableitung").

The letter

was

written while Einstein

was

working

on

Einstein 1916n

(Doc. 38),

which

repeats

the

argument

of

§2

of this

paper

and adds

important

new

results

as

well.

[9]See

Einstein

1905k.

[10]See,

e.g.,

Planck 1900a.

[11]Ernest Rutherford had described radioactive

decay

by

the

equation representing

such

a

"monomolecular"

process

as

early

as

1900 (see

Rutherford

1900).

[12]Such

calculations

were

indeed made

as soon as

both classical mechanics

and

classical

electrodynamics

had been

put

in

quantal

form

(see

Dirac

1927).

[13]For

the Wien

displacement

law in

appropriate

form,

see

Planck

1901a,

sec.

2.

[14]For

Einstein's earlier work

on

the law of

photochemical equivalence,

see

Einstein 1912b

(Vol. 4,

Doc.

2), 1912f (Vol. 4,

Doc.

5),

and 1913a

(Vol. 4,

Doc.

12);

see

also

Vol.

4,

the edi-

torial

note,

"Einstein

on

the Law of Photochemical

Equivalence,"

pp.

109-113,

for

a

discus-

sion.