Assertion (A):The line spectrum of each element is unique.

Reason (R):  Line spectrum consists of a limited number of lines each of which corresponds

to different wavelength.

Line spectrum is characteristic spectra of atom and atoms of element shows same property and spectrum is same

Reason: Line spectrum consists of different wave lengths

Ex: Na has two bright lines having wave length $5890\text{A}°\&5896\text{\hspace{0.17em}A}°$.