Single beam spectrometer is a fundamental analytical instrument used to measure the intensity of light at different wavelengths. It consists of a light source, a monochromator to select specific wavelengths, a sample holder, and a detector. Unlike double-beam spectrometers, it measures light intensity before and after the sample in separate steps, making it simpler and more cost-effective but requiring a reference measurement for comparison.

This type of spectrometer is widely used in chemistry, biology, and environmental science for applications like concentration determination, absorbance/transmittance analysis, and qualitative identification of compounds. Its advantages include compact design, ease of use, and affordability, though it may be less accurate for fluctuating light sources. Modern versions often integrate digital detectors and software for enhanced precision.

Due to its versatility, the single beam spectrometer remains a essential tool in laboratories for routine analysis and educational purposes.