Question

The cathode of a C.R.O. is usually coated with ------------- A. Alkali metals B. Tungsten or thorium oxide C. Copper oxide D. Barium or strontium oxide Answer :

Answer 1

Answer:

D) Barium of strontium oxide

Explanation:

The electron gun assembly of a CRO consists of an indirectly heated cathode, a control grid, a focusing anode and an accelerating anode and it is used to produce a focused beam of electrons.

The cathode consists of a nickel cylinder coated with oxide coating and provides a large number of electrons. It is associated with Barium or Strontium oxide.

Answer 2

The correct fill in the blank is D. Barium or strontium oxide

• The cathode is made out of a nickel cylinder with an oxide adequately covering that typically provides many mobile electrons.

• It is generally coated with the elements barium and strontium oxide.

• The work function of the cathode plate is further reduced to 1 eV when it is plastered with barium and strontium oxide, and it is only necessary to heat it to 1,000 K to naturally produce a significant supply of electrons.