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IV

1. The kinetic energy of the reaction is of course divided
   between the product particles, with the lion's share going to
   the lighter particle.

2. Small as the stars appear to us, there are many of
   them much larger and hotter than the sun.

59. Were the observations rigorously correct and the
values of the unknown quantities finally determined affected
by no error, they would be many times more accurate than
we can hope to make them.

60. It is suggested that a first section of each article should be devoted to a statement of the particular problem and to a short summary of its history and previous work, to be followed by the modern advances.

61. Most of the primary radicals may be expected to
react with monomer even in the presence of inhibitor, the
action of the latter being confined principally to the
termination of chain radicals of very short time.

1. Since the quantities e are equally likely to have positive
   or negative values, the sum of the terms in the last line is
   as likely to be positive as negative.

2. Turning to the metal phthalacyanides, we find all of
   the above authors reporting observation of electrical
   conductivity.

1. The records show three separate groups of waves.
   The first to arrive are waves in which the vibrations are
   predominantly longitudinal.

2. These corpuscles have either no electric charge and
   mass, or at any rate a charge and mass negligible as compared
   with those of the electrons, minute as the latter are.

3. Alternatively, both antennas can be located at fixed
   positions, with provisions being made to rotate the antenna
   under test.

4. The half-life period is the number of seconds for the
   activity to fall to half its original value, i. e. for half the
   atoms to break up.

210

V

68. Note that this effect does not necessitate complete
occupancy of the lower conduction levels, but only that the
density of states corresponding to the absorption constant
considered should occur at a higher energy.

69. The numbers given for the atomic weights must not
be taken to represent the actual weights in, say, grams or
pounds but rather as being proportional to them.

70. The point of view to which the number of objections
is minimum is the assumption that the electron, exhibiting
as it does both wave and corpuscular properties, consists of
a fortuitous conglomeration or concentration of waves of
different frequency as in Fig. 4—4.

71. It is possible to calculate to a fair degree of accuracy what should be the conductivity 'of the perfect crystal (at 0°K) of germanium or silicon when it is brought up to room temperature, say 300 °K.

1. Nineteenth-century physics succeeded in achieving
   the complete domination of the phenomena we observe
   around us.

2. Another case where the motion of the electron is not
   presumed by Wave Mechanics to follow the classical laws
   of motion is when its associated wave meets with obstacles
   in the path of propagation.

74. There are several precautions to be observed in making
such experiments.

75. Actually this theory, attractive as it is in its simplicity,
leads to a model of the photon having, so to put it, only
half the symmetry of the real photon.

76. Becquerel's discovery in 1896 was followed by the studies made by Rutherford, Soddy and Curie.

77. Preliminary qualitative experiments showed gradual
addition of dilute alkali hydroxide to a solution of chromous
chromide to result in the precipitation of a bluewhite basic
salt.

VI

78. Chemists have worked out an orderly fashion at least
for the more common anions such as arsenates, borates,
carbonates, halides, nitrates, phosphates and sulphates, to
mention only a few out of a list of hundreds of salts.

211

1. It was only after Rutherford's discovery in 1911 that
   an atom consists of a small, massive, positively charged
   nucleus surrounded by electrons, that the theory could be
   applied to quantitative description of atoms.

2. Because of the soft, large-grain structure of bismuth,
   it was a major purpose to produce a mirror surface that
   would not spread the neutron beam, and considerably more
   difficult to obtain one that would retain this surface after
   immersion in liquid oxygen.

3. Suppose fission is possible; then if it is to take place,
   the system must pass from A to D. The obvious way for it
   to do so is for the incident neutron or other particle, to
   supply enough energy to bring that of the resulting compound
   nucleus to a point lying above C.

82. General rules predicting the direction in which a process is influenced by outer forces are very desirable from a practical point of view.

1. While an ad hoc theory usually fits the facts, it is
   frowned upon by the scientific world, because in nearly all
   cases of such theories, it is not long before additional data
   are discovered which the theory, made to fit only a specific
   set of facts, fails to explain.

2. All too brief as this survey is, it will have shown that
   laboratory research during the last few years has led to results
   of the utmost interest almost each day.

85. While many more, and much more accurate
experiments will be needed, it is reasonably clear which kinds
of experiments are most likely to contribute significant
information.

1. Plutonium — 239 is obtained from uranium — 238,
   as a result of radioactive capture of neutrons released in
   reactors, followed by two relatively rapid stages of beta decay,
   as stated above.

2. Although the alloys contained only copper and gallium,
   the effects of the other elements likely to be present with gallium were also examined.

VII

88. Dry ashing and extraction of the ash is followed by
photometric determination of the catalytic influence of the
Ce—As reaction.

212

1. The following example indicates the main features to
   be considered when one decides whether to use correlation
   or spectral analysis for a particular problem.

2. It was not until ten years after Bohr had predicted
   correctly the energy states of hydrogen that the energy of
   hellium in its ground state was calculated by Kramers on
   Bohr's theory.

3. Their emission spectrum whether excited by light or
   by alpha particles is quite different from that of pure
   luminescent zinc-sulphate, the colours being green and blue
   respectively.

92. It is common practice to designate the electrodes by e, с and b — emitter, collector and base. The practice will be followed in this book.

1. Should the exciton remain at the particular atom,
   both this atom and its neighbours would shift their positions
   to new equilibrium values, emitting phonons during the
   process.

2. The energy gap is responsible for semiconductors
   being opaque and having metallic reflection in the optical
   region.

95. More generally, a sufficient (but perhaps not necessary)
condition for the Born approximation to be valid would be
that the exponential decay length a^-1 of the wave function
of the picked-up particle outside the nucleus be at least as
large as nuclear radius.

1. Instead of observing a crystal while it is growing
   another approach for studies is to observe the crystal surfaces
   on which growth has been arrested. With this method of
   observation much better techniques can be employed which
   are therefore likely to yield more information.

2. It is the property of electrons to radiate energy when
   accelerated that accounts for many ot the properties of the
   layer in the upper atmosphere.

3. The theory in question assumes the variation in
   conductivity on illumination to result from changes in n,
   the density of conductivity, electrons or holes, as the case
   may be.

4. To put the question in another way, how can the
   presence of a slit through which a photon does not go prevent
   that proton from reaching a part of the screen it would be
   likely to reach if tthat slit were closed?

213

100. The streams of ionized particles assumed to be
emitted at the time of flares and to escape sometimes from
the soler atmosphere and reach the Earth, giving rise to
sudden magnetic storm, also have velocities of the right order.

101. Counterbalancing the rate of energy generation are
various mechanisms of energy loss from the reaction region.

102. Hydrogen undergoes fusion at a much slower rate
that would deuterium or tritium under the same conditions.

103. It is not generally appreciated that during this period
there appeared to be possibilities of crystal amplifiers and
crystal oscillators becoming practical devices.

104. Finally one must remark that, whatever validity an application of the principle of equipartition may possess, it must be applied with caution to a rotating system.

1. If retardation did not occur all tin objects would be
   recrystallized each time the temperature cooled below 13.2 °C
   and would rapidly disintegrate to powder.

2. This hypothesis, startling as it may seem at first
   sight, appears, none the less, to contain a considerable element
   of truth.

3. With equation of state adopted, with the virtual
   coefficient assumed constant for a particular gas, the heat
   capacity at constant volume is independent of the pressure.

108. The transistor followed by a phaseinverting
transformer, and the neutralyzing network are connected in
parallel at both input and output terminal pairs.

109. Included in this group are atmospheres containing
gasoline and other gases of similar hazard.

110. No complete and quantitative theory of
photoconductivity has yet been developed, nor, from the very
complexity of the problem, is an early solution to be expected.

111. The usual approximation is semiconductor statistics
corresponds to the second term in the brackets of (3.8)
being negligible.

112. By 1910 Planck's quantum theory and Einstein's
photoelectric equation together with various lines of
experimental evidence had made it clear that, impossible as
it then seemed, physicists would perhaps have to accept the
hypothesis that light itself possesses corpuscular charac­
teristics.

113. A plate of conductivity g1 is followed by a second
plate of nearly infinite conductivity.

214

114. The last controlled experiment to be performed on
the gas would be a study of the relationship between
temperature and pressure, the volume being kept constant.

1. In order to calculate the excitation energy, the
   well-known semiempirical atomic mass formula is corrected
   for its deviations known to be attributed to the effects of
   nuclear shells.

2. Daring as at first sight this hypothesis appears to
   be, there is nevertheless a whole series of experiments which
   seem scarcely possible to explain on the wave theory, but
   which can be understood at once if we accept the hypothesis
   of the light quantum.

3. It is only through the general law of averages that
   we can expect the effect of these fortuitous but systematic
   errors to be completely eliminated.

4. The product of С and C1 (time constant) should be
   equal to or greater than the inverse of the lowest frequency
   to be amplified by the stage.

5. A particle which is acted upon by a force which
   varies directly with the distance from a fixed point will, if
   displaced and released, execute a motion represented by the
   above equation if no other forces, such as friction, come
   into play.

6. Owing to the measures of A being made around the
   pole as an axis, the apparent displacement due to a
   given A A is less, the nearer the direction of the point p is
   to that of the pole, the general law being: displacement —
   cos .

7. The old theory of heat which considered heat to be
   a fluid could not explain why two pieces of ice could be
   made to melt when rubbed against each other.

8. To complete the parallelism with the photonfield
   case, the energy and momentum of the particle are also
   related to the frequences and wave number of the wave
   function according to equation.

9. The theory of propagation of the detonation wave
   was worked out first of all to account for observations made
   on the speed of gas explosion.

10. By absorption of photons of higher frequency and
    therefore greater energy content, electrons of correspondingly
    greater velocity should be produced as was found to be
    invariably the case.

215

1. It is found to be easy to arrange experiments in
   which the loss of conductivity during the time the ions are
   in the gas is due principally to the process of recombination.

2. Light is considered to be a hail of light quanta,
   which knock out an electron the moment they strike a metal
   particle.

3. I shall merely draw attention to the majestic curve
   which physical theory would have described, were this new
   theory to receive definite confirmation.

4. Different as they may appear at first sight, the two
   forms of the new Mechanics are found to coincide in the
   last analysis.

5. Careful experiment showed that electrolytes obeyed
   Ohm's law, the current being proportional to the e. m, f. no
   matter how small the latter might be.

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