Nuar Josh BOlton and Justyn Day The Discovery of the Electron Cathode Ray Tube What was the composition and properties of this mysterious ray Inventor Karl Ferdinand Braun 1897 Specialized vacuum ID: 235353
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Slide1
A Presentation by Bernard Nuar, Josh BOlton, and Justyn Day
The Discovery of the ElectronSlide2
Cathode Ray Tube
What
was the composition and properties of this mysterious ray
?
Inventor: Karl Ferdinand Braun 1897
Specialized vacuum tubeThe cathode ray produced a bright green light
How does it work?Slide3
The Initial Question
Sir William Crookes (1832-1919)
Did these cathode rays have particle or wave like properties?
Made his own specialized Crookes tube
Maltese Cross
How did the cathode ray interact with the solid cross?
What does this mean?
Therefore, the cathode ray has
particle
like behavior!Slide4
Magnetic fields
Julius Plücker
(1801-1868)
Discovered that cathode ray was affected by magnetic forces
Jean Baptiste Perrin
(1870-1942)
Perrin is given credit for having discovered that the particles that made up the cathode ray were negatively charged
The beam is deflected towards the positive end of the magnetSlide5
Heinrich HertzFound that the electron passed through thin gold sheets and illuminated on the other side
First to apply an electric field to manipulate rays path
Failed to manipulate the rays with electric fields.
Brought the gold sheet observation to Thomson’s attentionSlide6
J.J. ThomsonRegarded as father of the electron
Proved the electron is manipulated by electric fields with lower pressures, which Hertz failed to do
How did he do this?
He replicated and confirmed the results of previous experiments
Calculated the charge to mass ratio of the electronSlide7
J.J. Thomson’s cathode
Without an electric field
With an electric fieldSlide8
E/M Derivation
N: number of particles in a cross section of the beam
m
: Mass of the particle
v
: Velocity
W: kinetic energy of the particle
H: Magnetic field
ρ: Radius of curvature
e
: Charge of an electron
I: Current
Q: quantity of electricity carried by the particles
Q=Ne
What were his findings?
e/m = 1.7 x
10^7
About 1/1700 the ratio of Hydrogen!Slide9
Thomson’s Theories
Three theories based on experimental observation
Cathode rays are charged particles, “corpuscles”
These corpuscles were constituent of atoms
These corpuscles are the only constituents of atoms (was later proven wrong)
The name corpuscles was later replaced with the term electronSlide10
Impact of the Findings
The cathode ray was composed of electrons with particle like properties
The electron charge to mass ratio was smaller than the hydrogen atom
It had a negative charge
There must be an opposite charge to maintain electrically neutral atom
Made possible the Plum Pudding model of the atomIt made possible new technologies and advancements in scientific fields Slide11
What this discovery gave us:
The electron is very important for many things we all use:
Emergence of new sciences made possible:
Quantum Physics
Large Particle Accelerators
Modern ChemistrySlide12
Questions