the nobel prize in physics 1923 - ustcstaff.ustc.edu.cn/~xjun/transparencies02.pdf · 2013. 3....

Robert A. Millikan (22 March 1868 –

19 December 1953)

The Nobel Prize in Physics 1923

…I went out to the drug store that

afternoon and bought an atomizer and

some watch oil. Then I came back to

the laboratory and set up the following

apparatus:

… I saw a most beautiful sight. The field

was full of little starlets….

Millikan, The isolation of an Ion, a Precision Measurements of its Charge,

and the Correction of Stokes’s Law, Science, 1910

J. J. Thomson, (18 December 1856 – 30 August 1940)

The Nobel Prize in Physics 1906

plum-pudding model

Ernest Rutherford

30 August 1871 – 19 October 1937

The Nobel Prize in Chemistry 1908

"for his investigations into the disintegration of the elements, and the chemistry of radioactive substances"

Geiger–Marsden experiment

Geiger H. & Marsden E. (1909). "On a Diffuse Reflection of the α-Particles". Proceedings of the Royal Society, Series A 82: 495-500

“It was quite the most incredible event that has ever happened to

me in my life. It was almost as incredible as if you fired a 15-inch

shell at a piece of tissue paper and it came back and hit you. “

—Ernest Rutherford

Fc

rR

Fc

rR

E. Rutherford, The Scattering of α and β Particles by Matter and the Structure of the Atom, Philosophical Magazine. Series 6, vol. 21. May 1911

H. GEIGER and E. MARSDEN, The Laws of Deflexion of a Particles through Large Angles, Philosophical Magazine, Series 6, Volume 25, Number 148, April 1913

(1) Variation with angle. (2) Variation with thickness of scattering material. (3) Variation with velocity of incident a particles. (4) Variation with atomic weight of scattering material.

Angle

f

Scintillations per minute.

1

--------

sin4f

N x (sin4f / 2) Without

foil.

With

foil.

Corrected

for effect

without

foil.

Corrected

for decay,

N.

150 0.2 4.95 4.75 6.95 1.15 6.0

135 2.6 8.3 5.7 8.35 1.38 6.1

120 3.8 10.3 6.5 9.5 1.79 5.3

105 0.6 10.6 10.0 14.6 2.53 5.8

75 0.0 28.6 28.6 41.9 7.25 5.8

60 0.3 69.2 68.9 101 16.0 6.3

(1) Variation with angle

(2) Variation with thickness of scattering material.

I.

Number of

sheets of

mica

II.

Range R of a

particles after

leaving mica

III.

Relative

values of 1/n4

IV.

Number N of

scintillations

per minute.

V.

Nn4

0 5.5 1.0 24.7 25

1 4.76 1.-21 29.0 24

2 4.05 1.50 33.4 22

3 3.32 1.91 44 23

4 2.51 2.84 81 28

5 1.84 4.32 101 23

6 1.04 9.22 255 28

(3) Variation with velocity of incident a particles.

I.

Substance.

II.

Atomic

weight

.

A.

III.

Air

equivalen

t

in cm.

IV.

Number of

scintillations

per minute

corrected

for

decay

V.

Number N

of

scintillations

per cm. air

equivalent.

VI.

A3/2.

VII.

N x A3/2.

Gold....... 197 0.229 133 581 2770 0.21

Tin......... 119 0.441 119 270 1300 0.21

Silver...... 107.9 0.262 51.7 198 1120 0.18

Copper.... 63.6 0.616 71 115 507 0.23

Aluminium. 27.1 2.05 71 34.6 141 0.24

(4) Variation with atomic weight of scattering material.