4.1 Thermionic Emission

Process of emission of electrons from hot metal surfaces is called .................

• photoelectric effect

• thermionic emission

• static emission

• emission current

Which particle escapes from the surface of the metal when it is heated at a high temperature?

• Proton

• Neutron

• Nucleon

• Electron

Electrons have a positive charge.

• True
• False

Which particle is cathode ray?

• Electron beam

• Gamma ray

• Neutron

• Alpha particles

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

Cathode rays carry ..........

• negative charge

• positvie charge

• neutral particles

• electrons and protons

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

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 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.