Question

The spectrum of white ranging from red to violet is called continuous spectrum because:
(A) Different colours are seen as different bands in the spectrum.
(B) The colours continuously absorb energy to form a spectrum.
(C) The violet colour merges into blue, blue into green, green into yellow and so on.
(D) It is a continuous band of coloured and white light separating them.

Answer 1

Hint: The electromagnetic spectrum is usually of two types continuous and discrete. A discrete spectra forms when some frequencies are absent in a spectra. A continuous spectra forms when radiations are absorbed and emitted at all frequencies.

 Complete answer:
Spectra of white light is obtained when a hot body releases its energy in the form of radiations. Also when we excite a body with external radiation, we observe that the body absorbs the radiations of particular frequency. White light is usually obtained from the spectra of the Sun. It emits radiations over a wide range of frequencies. The light obtained if is made to pass through a prism, separates into seven colours from red to violet. The spectra obtained is a continuous one, we observe that in the range from red to violet, all frequencies are present.

 The correct answer is option (C) as there is no separation between the components obtained.

 Additional information:
Light interacts with matter in a manner such that when light falls on the matter, the atoms of the matter absorb radiations of certain kinds to which there are exact energy difference levels in the atom. The atom then re-emits those energies in the form of radiations of those frequencies.

 Note:
Since in white light, we are talking about the emission spectra, therefore option (B) becomes invalid for our case. Option (D) is incorrect because the white light does not separate components. The components become visible when the light passes through a device like a prism. Option (A) describes a band spectrum. The separation is not spatial here. We are talking about the frequency separation mostly.