A modified discharge tube is used as a __________
A) Cathode ray oscilloscope
B) Fluorescent tube
C) X-ray tube
D) All the above.

Hint:As the temperature of a group of atoms increases, their collisions become more violent and a large fraction of them are promoted to the excited states. Since there are more exciting atoms; more photons are emitted as the atom becomes de-excited.

Complete step by step answer:
A discharge tube is a tube containing charged electrodes and filled with a gas in which ionization is induced by an electric field. The oscilloscope of X-ray tubes, fluorescent tubes and cathode rays can be used as a modified discharge tube containing charged electrodes in these tubes and filled with gas.

Discharge tubes can be used to avoid the flow of current below a certain voltage; by using ionising gas that glows through the tube as current flows, they can also act as lamps.

A closed, low-pressure insulating vessel containing gas through which an electrical current flows when its electrodes are applied with an appropriate voltage.

Electrons accelerated to high speeds travel through an empty cathode ray tube in straight lines and reach the tube's glass wall, inducing fluorescence or glow in excited atoms.
Cathode rays carry electric currents through the tube.

The constituents of cathode rays were first discovered as electrons. The cathode ray tube was used by J.J. Thomson established that atoms had small particles within them that were negatively charged, called "electrons."

X-rays are generated within the tube anode via the interactions of accelerated electrons with electrons of tungsten nuclei. Researchers noticed that something was travelling from the anode when objects positioned in the tube in front of it might cast a shadow on the glowing wall.

The x-ray tube is a simple electrical device usually containing two principal elements: a cathode and an anode. The electrons experience an energy loss as the electric current passes through the tube from cathode to anode, resulting in x-radiation generation.

From these observations, we can say that option (D) is correct.

Note:
-Two types of X-ray are generated: characteristic radiation and radiation of bremsstrahlung.
-If an electron jumps from lower level to higher orbit, it will absorb energy.