ideas to implementation

Electron Tube - TV

a

Discharge tubes

Cathode Rays - Particle

E B balance e/m

r

F = Eq...........................................(1)F =qvB..........................................(2)F=mv^2/r (with no electric field).......(3)also E= V/d(1) = (2) gives v(2) = (3) + v + r measured gives e/mor (1) = (2) = (3) gives q/m = E/rB^2

Applications

r

•outline the role of: ◦electrodes in the electron gun◦the deflection plates or coils◦the fluorescent screenin the cathode ray tube of conventional TV displays and oscilloscopes

Electron gun and Plates

r

Electron gun has a very high field as the lines converge on a point. Heat also kicks the electrons of the tip. The acceleration anode give the electrons a high fixed speed, which provides the energy that is later converted into light.Further Plates act as an electrostatic lens that curves electrons moving at an angle to the axis back into form an image of the gun on the screen.

CRO

r

Single gun, with focus designed for steady intensity.

Old Television

r

Three guns for three colours, and designed to switch current pixel to pixel

Deflection

CRO

r

Internal E field Plates, Expensive, but highly sensitive for science

Old Televisions

r

External Coils, Cheaper but designed to "RASTER"

fluorescent screen

r

Makes light when hit with electrons

CrO

r

Single colour green or blue to read at close distance

Old Television

r

Colour TV has clusters of three phosphors for observation at a distance

Production of electrons with light - solar cells

a

Semiconductor

a

Superconductor

a

Bragg

r

outline the methods used by the Braggs to determine crystal structureBragg used x-rays (100 ev Photons)X-rays are made by electrons smashing metalsx-rays reflect of atomsspaced atoms cause interference

a

Conduction and resistance

Conduction

Resistance