When electric field is applied between cathode annd anode, at pressure of about 0.001 mm of mercury in a discharge tube, following is observed.

Options

A. There is no discharge in the tube
B. A zig-zag thin red spark runs from cathode to anode
C. whole of tube is filled with bright light
D. a fluorescent glow appeared on the glass opposite to cathode

Answer

D

Explanation

It was found that at sufficiently low pressure of about 0.001 mm of merury column, a discharge took place between the two electrodes on applying the electric field to the gas. A fluorescent glow appreared on the glass opposite to cathode.