Question

An ordinary tube light used for lighting purposes contains:
 A. Fluorescent material and an inert gas
B. One filament, reflecting material and mercury vapour.
C. Fluorescent material and mercury vapour.
D. Two filaments, fluorescent material and mercury vapour.

Answer 1

Hint: A tube that is made of low vapour pressure of mercury gas and which is a gas discharge lamp that uses fluorescence to produce light. When electric current strikes the mercury vapour, a glow light is produced which is responsible for lighting.

Complete step by step answer:
The bunch of electrons collides with the mercury gas and hence the atoms of mercury gain energy and emit UV light which then strikes the inside coating of the tube. The UV light inside strikes the inner material of the tube which is fluorescent and which converts UV light to visible light. Calcium chlorophosphate is one of the fluorescent materials.

The same idea lies in television pictures. The TV screen consists of tiny dots of fluorescence which when struck by the electron produce the pictures. The small dots consist of different colours. When an electron becomes critically excited and then returns back to the ground state, then it emits a sparkling wavelength of light which is called fluorescence.

A general light tube has double filaments, a material which is fluorescent and the vapour of mercury.

So, the correct answer is “Option D”.

Note:
 The phenomenon of fluorescence is also used in spectroscopy which is used as a diagnostic tool for the fast and forward diagnostic ability in the field of microbiology. This spectroscopy has high sensitivity and high specific rate. Nowadays this technique is getting more popularity as compared to x-rays as exposure to x-rays can cause severe cancer.