Thermionic Emission

one of the properties of cathode rays is

• positive charge

• does not move in a straight line

• can be deflected by electrical field

• cannot be deflected by magnetic field

If an electric field is put across the beam with the positive plate on top and the negative plate below.

The beam will bend

• Up

• down

• left

• right

• in a circle

I use thermionic emission to emit a stream of electrons and display them on a screen.

• Cathode-Ray Oscilloscope

• Raster-Scan Display

• Random-Scan Display

Process of emission of electrons from hot metal surfaces is called

• photoelectric effect

• thermionic emission

• static emission

• emission current

Particles emitted from a hot cathode surface are:

• negative ions

• photon

• protons

• electrons

Cathode rays carry

• negative charge

• positvie charge

• neutral particles

• electrons and protons

Cathode rays can be deflected by

• electric fields only

• magnetic fields only

• quantum fields

• magnetic and electric fields

Why is a vacuum needed in the tube?

• It makes the process more efficient.

• It impedes or slows down the electrons.

• It allows the electrons to flow unimpeded.

• It allows the electrons to be made into a beam.

How are the electrons made into a beam?

• Using a high voltage across the tube.

• Use of an anode to spread the electrons.

• Use of positive anode to focus the electrons.

• Use of a fluorescent coating at the end of the tube.

How is the electron beam detected?

• Use of a fluorescent screen.

• By deflecting the beam of electrons with a magnetic field.

• By deflecting the beam of electrons with an electric field.

• Using an electron microscope.