Chemistry · Structure Of Atom · NEET
A continuous spectrum has ALL wavelengths present, so the colours blend smoothly with no gaps (violet to red, like a rainbow). A line spectrum has only CERTAIN wavelengths, so you see a few bright coloured lines separated by dark spaces. Simple test: if there are gaps (dark regions), it is a line spectrum; if there are no gaps, it is continuous.
A rainbow is a continuous spectrum. White sunlight contains every wavelength in the visible range. When it passes through water droplets (which act like a prism), the colours spread out and merge into each other with no dark gaps. That smooth blend is exactly what NCERT calls a continuous spectrum.
When you pass an electric discharge through hydrogen gas, the atoms get excited and their electrons jump to higher energy levels. When the electrons fall back, they release energy of only fixed (discrete) values, because the energy levels are quantised. Each fixed energy = one fixed wavelength = one sharp line. Since only certain jumps are allowed, you get only certain lines, not every colour. This is why atomic spectra are line spectra.
You need a source that emits all wavelengths. White light from the sun or a hot glowing solid (like a bulb filament) gives a continuous spectrum. A single gas of one element cannot, because its atoms only emit a few fixed wavelengths, which gives lines instead.
Both are line spectra for an element. In an EMISSION spectrum, excited atoms give out light, so you see bright coloured lines on a dark background. In an ABSORPTION spectrum, white light passes through cool gas and the atoms absorb the same wavelengths, so you see dark lines on a bright continuous background. The lines appear at the exact same positions in both.
NCERT says each element has a unique line emission spectrum. No two elements produce lines at exactly the same set of wavelengths. So by matching the lines, scientists can identify an unknown element, just like fingerprints identify a person. Helium was actually discovered in the sun this way.
Try the real previous-year questions from this chapter — each with the answer and a full solution.
A continuous spectrum, ranging smoothly from violet (higher frequency) to red (lower frequency) with no gaps.
A line spectrum. It emits radiation of only certain discrete frequencies, seen as separate bright lines (for example, the Balmer series in the visible region).
Yes. Atoms of an element produce line spectra, which is why atomic spectra are also called line spectra. Continuous spectra come from white light or hot glowing solids, not from single-element gases.
Yes. The dark gaps are wavelengths the atom does not emit. The atom only releases energy of fixed values because its energy levels are quantised, so only a few wavelengths appear.
It is the base for the whole hydrogen spectrum, Rydberg formula, and Bohr model. NEET often tests whether you can tell continuous from line spectra and link line spectra to quantised energy levels.
