A system of physical chemistry - Index of

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A system of physical chemistry - Index of

PLANCK'S LATER QUANTUM HYPOTHESLS 49

When T = o, U is not = o, but = — This " residual energy " re-

mains with the oscillator even at 0° absolute. It cannot lose it since

"

it cannot emit anything less than one hv. At high temperatures and

for long waves in the region where the Jeans- Rayleigh Law holds the

new formula passes into the old."

For short waves (visible and ultra-violet «?''WAt

region) becomes

large compared with unity, and we have—

U = ^i".

2

As regards the question of the specific heats of solids considered in

the it is

following chapter, pointed out by Planck that measurements of

specific heat cannot be used to compare the older and newer forms of

"Q since C„ is dV/dT, and differentiation removes the additional term

— . Planck doubts whether the new expression can be tested experi-

2

direct means. ^

mentally by any

Up to this point the most important experimental evidence which

we have considered in support of the quantum theory is the fact that

Planck's radiation formula quantitatively reproduces experimental values

over the entire range of the spectrum investigated. In the next chapter

we shall deal with further experimental evidence in connection with the

atomic heats of solids which likewise is strongly in favour of the con-

cept of quanta.

' Planck refers to a paper by Stark (Phys. Zeitsch., 9, 767 (1908)), on the

application of the quantum theory to canal rays. As regards an attempt to distingui.sh

between the old and new form of the quantum theory, see A. Einstein and

O. Stern {Annalen der Physik, [4], 40, 551, 1913).

VOL. III.

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