Line sources are used for both UV and visible in spectroscopy. Which pair is used?

Line sources are used for both UV and visible in spectroscopy. Which pair is used?

• A. Tungsten Halogen Lamps
• B. Mercury and Sodium Vapor Lamps
• C. Hollow Cathode Lamp
• D. Xenon Arc Lamp

Answer: (B)

In spectroscopy, line sources emit specific, sharp wavelengths rather than a continuous spectrum, making them ideal for calibrating wavelengths and identifying spectral features in the UV and visible regions. Mercury lamps produce several well-known emission lines in both the ultraviolet and visible parts of the spectrum, giving reliable reference points across a broad range. Sodium vapor lamps contribute a very intense, narrow line near 589 nm (the sodium D-line), which is one of the most familiar and precise calibration features in the visible region. Together, these two sources span UV and visible with strong, discrete lines, making them the standard pair for line-source applications. Tungsten halogen lamps are broad-spectrum (continuum) sources, not line sources. Xenon arc lamps also act more like continuum/line-rich sources but are not as clean or widely used for precise line calibration as the mercury and sodium combination. Hollow cathode lamps are excellent line sources for specific elements, but they’re element-specific rather than providing a broad, ready-to-use UV/visible calibration set.

In spectroscopy, line sources emit specific, sharp wavelengths rather than a continuous spectrum, making them ideal for calibrating wavelengths and identifying spectral features in the UV and visible regions. Mercury lamps produce several well-known emission lines in both the ultraviolet and visible parts of the spectrum, giving reliable reference points across a broad range. Sodium vapor lamps contribute a very intense, narrow line near 589 nm (the sodium D-line), which is one of the most familiar and precise calibration features in the visible region. Together, these two sources span UV and visible with strong, discrete lines, making them the standard pair for line-source applications.

Tungsten halogen lamps are broad-spectrum (continuum) sources, not line sources. Xenon arc lamps also act more like continuum/line-rich sources but are not as clean or widely used for precise line calibration as the mercury and sodium combination. Hollow cathode lamps are excellent line sources for specific elements, but they’re element-specific rather than providing a broad, ready-to-use UV/visible calibration set.