BharatNotes Spectrum
noun (plural: spectra, also spectrums)Usage in a UPSC answer
Far from being a binary contest between the state and the market, India's development debate occupies a broad spectrum of positions, ranging from welfarist redistribution at one pole to laissez-faire reform at the other, and prudent policy must accommodate this plurality rather than collapse it.
Synonyms
Antonyms
Word Family
spectra (n pl), spectral (adj), spectrometer (n), spectroscopy (n), spectroscopic (adj)
Root
Latin spectrum = image, apparition; Latin specere = to look at; -trum = instrumental noun suffix
Etymology
From Latin spectrum ("image, apparition"), from specere ("to look at"); first used in an optical sense by Isaac Newton in 1671.
Memory Hook
Linked to "spectacles" and "inspect" — all from Latin specere "to look": a spectrum is the full sight you behold when light is spread out, hence the whole visible range of anything.
How This Word Works in UPSC Writing
The array of components obtained when a wave is separated by wavelength. The visible spectrum from violet to red is only the narrow band the eye detects, and a prism produces it because refractive index varies with wavelength, so violet bends most and red least. The electromagnetic spectrum is the full range, running from radio waves through microwave, infrared, visible, ultraviolet and X-rays to gamma rays, all travelling at the same speed in vacuum and differing only in wavelength and frequency. Holding that order makes several environmental facts specific rather than vague, since it is ultraviolet that the ozone layer absorbs and infrared that greenhouse gases trap. Spectra are also diagnostic, which is the deeper point: a hot solid gives a continuous spectrum, an excited gas gives bright emission lines unique to each element, and a cooler gas in front of a hot source gives dark absorption lines, which is how the composition of stars is known without visiting them.
Don’t Confuse It With
The visible spectrum is the narrow band the eye can detect, while the electromagnetic spectrum is the complete range from radio waves to gamma rays. Dispersion is the process that produces a spectrum, and the spectrum is its result. An emission spectrum shows bright lines characteristic of an excited element, while an absorption spectrum shows dark lines at exactly those wavelengths, so the two are complementary signatures of the same element. Note the separate telecommunications sense, where spectrum means the range of radio frequencies treated as a scarce public resource and allocated by the state.
Hindi Meaning
वर्णक्रम (varnakram) or स्पेक्ट्रम; विद्युत चुम्बकीय वर्णक्रम for the electromagnetic spectrum.
Common Questions
- What is the order of the electromagnetic spectrum?
- From longest to shortest wavelength: radio waves, microwaves, infrared, visible light, ultraviolet, X-rays and gamma rays.
- How do we know what stars are made of?
- From their absorption spectra, since each element removes light at a characteristic set of wavelengths, leaving dark lines that identify it.
Seen in UPSC Question Papers
- Prelims 2020 — IT & Cyber
Real UPSC previous-year questions whose text uses “Spectrum” — proof this word earns its place on your list.
Tip: press Alt+S to hear pronunciation
