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

Particles emitted from a hot cathode surface are:

• negative ions

• photon

• protons

• electrons

Cathode rays can be deflected by

• electric fields only

• magnetic fields only

• quantum fields

• magnetic and electric fields

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.

what happens when cathode rays strike the fluorescent screen

• electron bounces back

• nothing happens

• emit light

• produce current

what happen to the electron when when it is emitted from the cathode or metal?

• move around the cathode

• attract toward the anode

• attract toward the cathode

• goes back to cathode to form equilibrium state

what is the purpose of connecting anode with high voltage d.c power supply

• to deflect or change the direction of the electron

• to accelerate the electron

• to deceleration the electron

• to increase the rate of thermionic emission

For what are cathode ray tubes used ?

• Oscilloscope.

• old style TV pre 2000

• old computer monitors pre 2000

• all of the above

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