Question

Line spectrum is obtained from the:
A) Sun
B) Filament of the bulb
C) Mercury lamp
D) Burning coal

Answer 1

Hint: The solution of the given question is totally based on the understanding of line spectrum. First of all we need to know about the spectrum and then about the line spectrum. Also, we need to gather information about the production of the line spectrum and the sources of its production. Then finally, we can conclude with its solution.

Complete answer:
First of all, let us understand the spectrum. We can define spectrum as a beam of light that can be separated in the form of light waves or radio waves. The common example of visible spectrum is the rainbow in which we are able to see different colours separated by a thin boundary.
Now, let us find the line spectrum. We can define a line spectrum as a dark or bright line which results either from the emission or absorption of light in a narrow frequency range.
Now let us discuss how a line spectrum is produced. When there is an interaction between atoms, molecules and a photon of specific frequency, it creates a line spectrum in which the photon is absorbed by the electron and is detected by an observer as a separate line.
Line spectrum can be emitted from arc lamps or other systems in the form of electrical discharge in a sealed gas tube. Neon lamps, hollow cathode lamps, electrode less lamps are some of the examples through which line spectrum can be emitted.
As it can be seen in step two that the source of emission of line spectrum is a sealed gas tube, so from the given options, mercury lamp satisfies this criteria.

Hence, option (C), i.e. Mercury lamp is the correct choice for the given question.

Note: We should not get confused with the filament of the bulb, as it is just a part of the bulb. If in the option it would have been given only a bulb, in that case it can be considered as a source of line spectrum emission. The spectrum of different wavelengths are classified as different bands and known as electromagnetic spectrum range.