Final answer:
A spectrum is the range of wavelengths emitted or absorbed by an object, characterized by line, absorption, and continuous spectra, corresponding to electromagnetic radiation from atoms in excited states, the dark lines in an otherwise continuous spread of colors, and broad uninterrupted range of wavelengths, respectively.
Step-by-step explanation:
The term spectrum generally refers to B. the range of wavelengths emitted or absorbed by an object. When atoms or molecules absorb energy, electrons are excited to higher energy levels. Upon returning to lower energy levels, they emit electromagnetic radiation at specific, discrete wavelengths, resulting in a line spectrum. An absorption spectrum shows dark lines where light has been absorbed, overlaid on a continuous spectrum. Conversely, an emission spectrum displays bright lines at wavelengths where radiation has been emitted. The continuous spectrum consists of radiation of a broad range of wavelengths, not just discrete ones, and is often represented by a blackbody, an object that perfectly absorbs all wavelengths of light that hit it.
When studying vast cosmic distances, scientists encounter the Doppler effect, where the observed wavelength of electromagnetic radiation changes due to the movement of the source relative to the observer. The complete range of all possible wavelengths of light is known as the electromagnetic spectrum, which includes radio waves, microwaves, infrared radiation, visible light, ultraviolet light, X-rays, and gamma rays.