Crookes tube

Text book says 90 degrees,

Look at this and you see near 90 degrees coming from a point and magnifying the shadow

Also seen is photo darkening of the glass when the cross is lowered.

There is an electron gun effect as the ionizing gas puts a plus charge cloud above the electrode.

Planck and Einstein

This is an original film of Planck during 1942.

This is a link to site that reviews Planck relationship with the Nazi's

A good article on Planck

His Noble speach

Crookes tube

This is an in depth review of the Crookes discharge tube.

4 Experiments with Crookes tubes
4.1 Maltese cross
4.2 Perpendicular emission
4.3 Deflection by electric fields
4.4 Deflection by magnetic fields
4.5 Paddlewheel
4.6 Charge
4.7 Canal rays
4.8 Doppler shift
4.9 Lenard window

Let me make it perfectly clear, the Jacaranda text book has so many errors in it, it is very clear the people writing it have not performed experiments or done even basic research.

Crooke built a basic vacuum tube with two electrodes. The word tube refers to glass bulb that is is connected to a vacuum pump. It is pumped out and put in an oven. The heat means any dirt is turned in to vapour and is pumped out. When the desired pressure is reached the glass tube connected to the vacuum pump is heated, atmosperic pressure closses the soft tube and it forms a sealed vacuum chamber.

This the closest image to heat sealing a tube

The syllabus say the pressure is 10-4 atm. I can tell you from making these devices the pressure is 10-7 atm and this the figure quoted in Wikapeadia

You can see clearly that the rays are emerging from a point in the centre of flat plate. The text book says this was taken as evidence of the wave rays emerging from the metal like a sound wave. However Wikipeadia states the if it was thought to be waves like light it would radiate like light in all directions light a electric light filament. Instead the particles followed the field lines. So they leave radially from a sphere, and straight out of a flat plate.

Why do the electrons leave from a single pit in the center of the flat electrode? The student who decided to sit at the back of the class and not look because it was boring is locked into a do loop.

I can answer this from my experiance working with Laser electrodes. Positive ions will pit the electrodes and this local curvature will create a local high field. If you want the entire electode to emit it has to be heated. This is exactly what you see in the demostration Cathode ray tube. When the metal heats up, it emits a uniform flow of electrons, but as before perpendicular from the surface. If you want an analogy the electrons flying the electric field are like rain falling down.

The emission of electrons from a hot metal is called "Thermionic" emission.

The fact that the shadow has crisp edges and is larger than the maltese cross shows also that the source of light is from a single point.

The process of glass or crystals glowing is called flouresence. The phosphor has a crystal stucture. When it is hit by an electron it emits light rather than heat. Glass and other disordered substance trap electrons in the random voids of the structure. There are not a large number of configurations of the matterial to rattle down and convert to heat, so the electrons inside the matterial change shape in a single leap emitting light. The process of the electrons moving in the voids of the glass shifts the voids creating path ways for the electrons to rattle down without creating light.

The blue glow in the Crookes space is from positive atom ions that recombine.

Why don't the electrons make a bee line to the positive electrode? They would if the vacuum tube was at really high vacuum the small amount of gas, become positively charged making it really a positive electrode just milimeters from the surface of the negative electrode.

Applications of Induction Motors

Discusses Induction Motors - Large dumb cheap and chearful

Web links

Flash showing discharge tube to spectra

HSC online

Syllabus

	Students learn to:	Students:
1. Increased understandings of cathode rays led to the development of television	explain why the apparent inconsistent behaviour of cathode rays caused debate as to whether they were charged particles or electromagnetic waves	perform an investigation and gather first-hand information to observe the occurrence of different striation patterns for different pressures in discharge tubes perform an investigation to demonstrate and identify properties of cathode rays using discharge tubes: – containing a maltese cross – containing electric plates – with a fluorescent display screen – containing a glass wheel – analyse the information gathered to determine the sign of the charge on cathode rays solve problem and analyse information using: F=qvBsintheta F=eV V=ED
	explain that cathode ray tubes allowed the manipulation of a stream of charged particles
	identify that moving charged particles in a magnetic field experience a force
	identify that charged plates produce an electric field
	describe quantitatively the force acting on a charge moving through a magnetic field
	discuss qualitatively the electric field strength due to a point charge, positive and negative charges and oppositely charged parallel plates
	describe quantitatively the electric field due to oppositely charged parallel plates
	outline Thomson's experiment to measure the charge/mass ratio of an electron
	outline the role of: – electrodes in the electron gun – the deflection plates or coils – the fluorescent screen in the cathode ray tube of conventional TV displays and oscilloscopes

Ideas to implementation- Context

9.4 From Ideas to Implementation

Contextual outline
By the beginning of the twentieth century, many of the pieces of the physics puzzle seemed to be falling into place. The wave model of light had successfully explained interference and diffraction, and wavelengths at the extremes of the visible spectrum had been estimated. The invention of a pump that would evacuate tubes to 10–4 atmospheres allowed the investigation of cathode rays. X-rays would soon be confirmed as electromagnetic radiation and patterns in the Periodic Table appeared to be nearly complete. The nature of cathode rays was resolved with the measurement of the charge on the electron soon to follow. There was a small number of experimental observations still unexplained but this, apparently complete, understanding of the world of the atom was about to be challenged.

The exploration of the atom was well and truly inward bound by this time and, as access to greater amounts of energy became available, the journey of physics moved further and further into the study of subatomic particles. Careful observation, analysis, imagination and creativity throughout the early part of the twentieth century developed a more complete picture of the nature of electromagnetic radiation and matter. The journey taken into the world of the atom has not remained isolated in laboratories. The phenomena discovered by physicists have, with increasing speed, been channelled into technologies, such as computers, to which society has ever-increasing access. These technologies have, in turn, often assisted physicists in their search for further knowledge and understanding of natural phenomena at the sub-atomic level.

This module increases students’ understanding of the history, nature and practice of physics and the applications and uses of physics, the implications of physics for society and the environment, and the current issues, research and developments in physics.