The Working Of An Double Beam UV- Visible Spectrophotometer

The visible instruments find a great variety of applications in the research and scientific laboratory.  One such optical device is the spectrometer and spectrophotometers that use the property of light rays to measure the specific wavelength.  The specific wavelength of light rays gets absorbed by the analyte present in the biological specimens.   These devices are also called analytical optical instruments. The main use of single and double beam spectrophotometers is to identify and confirm the presence of chemical species present within the biological specimens based on their chemical structures, the concentration of, etc.  One more specification is found in the double beam spectrophotometer is the double beam UV spectrophotometer.  This uses the light rays in their visible wavelength and measures in the same wavelength of light. 

The double beam UV vis spectrometer tends to emit the photons as light packets. These photons are then intended to pass through various biological specimens where the light beam is absorbed for measuring the biochemical entities’ presence.  The spectrophotometers measure the light intensities at different wavelengths through their precise instrumentation.

What Is A Double Beam UV-Visible Spectrophotometer?

A double beam UV visible spectrophotometer is somewhat the same as the double beam spectrophotometer in working.  In this double UV vis spectrophotometer, the light beam coming from the light source is split into two beams of light.  Like a double beam spectrophotometer, the monochromator is also present which selects the wavelength of light passing through the samples.  If the solution is of higher molecular concentration, then more light beams will get absorbed by the specimens.  Commonly, it is seen that when a sample is submitted for spectroscopic analysis, it should be all pure to avoid poor and imperfect results.

A typical double beam UV-visible spectrophotometer consists of :

  • A  light or energy source, which is typically a lamp.
  • A filter or a monochromator that is attached to the device for the selection of the wavelength of light.
  • A place for cuvettes to read the measurements

The detectors to get sufficient information from the spectroscopic analysis. It can be also a radiation detector or a phototube for detecting the change in the wavelength of light. This also helps in converting the energy received by the double beam Uv visible spectrophotometer into a measurable signal.

These signals are then taken into consideration for the inference of the data observed in the spectrophotometry process. In the arrangement of double beam Uv visible spectrophotometer, there are two types of optical conditions :

1. Single Beam  Spectrophotometer

It only emits light rays in a single beam.  The light source of this condition is the white light, that disperses from the disks of the spectrophotometer.

2. Double Beam Spectrophotometer

The single light beam is split into two beams for the diffraction process. Here, the monochromator plays its role by selecting the specific wavelengths of light for the spectrometry process.

In a double beam UV visible spectrophotometer, only light of a specific wavelength is extracted from the double beams or resulting spectrum.  The light rays are extracted from the exit slit opening of the spectrophotometer device.   The monochromatic light intensity irradiates the samples and intensity is detected.  In this way, the measurement is made. Hence, the transmittance of the light beams is done in the instrument. When it comes to the double beam arrangement, the same monochromatic light is split into two beams that pass through the samples placed at the pointing stage. Here, the measurements are done with a reference point set into the spectrophotometer for the measurement process and later on analysis.

Principle Behind A Double Beam UV-Visible Spectrophotometer

 A double beam Uv visible spectrophotometer works on the same principle as the single beam spectrophotometer and double beam spectrophotometer works. However, some additional phenomena of light rays do happen in the UV vis spectrophotometers. It makes them unique from the conventional ones and single and double beam spectrophotometers. 

The main working principles are as follows :

1. Dispersion Of Light Rays

The Example Of An Dispersion Process In An Double Beam UV Spectrophotometer.

Dispersion of light rays is well seen in nature,  just after the rain. The droplets diffract the sun’s light rays by creating a spectrum of color.  Here, the spectrum is called rainbow.  The same happens in the double beam Uv visible spectrophotometer where the diffraction of light happens through the specimens. The refraction of light makes the process of spectrophotometry more reproducible. In this instrument, the diffraction angles depend on the wavelength of the main incident light.  The disks are present in the instrument which helps in forming the angles of diffraction.  This gives rise to better measurements of the biochemical entities present in the sample.

2. Absorbance

Absorbance is usually defined as  the measurement of the ratio of incident light to transmitted radiant light rays through a biological sample during the spectrophotometry process. The cells present in the samples reflect the light and also absorb the same that gets transmitted to the detectors present in the instrument.  In the case of biological samples,  which scatter light, absorbance is defined as the ability of the sample to absorb more and more light passing through it.  The absorbance term is used in many technical areas to quantify the results obtained from the experimental measurement.   In a double beam Uv vis spectrophotometer, the absorbance is seen which is further used for the quantification of the results.

The term absorption is associated with the physical process of absorbing light in the spectrophotometry process, while absorbance is the ability of a sample to absorb the light.  It may also measure the attenuation of the lens used to the instrument, which is caused by absorption, in both single and double beam spectrophotometers.

3. The Visible spectrum Scattering Of Light Rays

In the spectrophotometric analysis in a double beam Uv vis device, when white light passes through the sample and is reflected by a colored substance, a portion of the mixed wavelengths is absorbed. The remaining light beam will be assumed the complementary color to the wavelength of light absorbed. This fact is demonstrated by the color spectrum.

After traveling through every part of the specimen cell or sample cell the light beams which does not get absorbed, most of them are directed onto the photo transducer or light detector in the double beam UV vis spectrophotometer. This part of the component converts the arrival of photons in the light rays into an electrical signal. This conversion is made through the computer screen. In this way, the light paths through the spectrophotometer need not be in a straight line. It can be disarrayed also. As it is seen that the light beam of rays can be redirected using mirrors in the device and can also be scattered through the help of a collimator.


The double beam Uv visible spectrophotometer helps to analyze the various biological specimens for good results. The electromagnetic spectrum is also used in the process of making measurements out of samples.  The dispersion, reflection, refraction all processes happen in the spectrophotometry devices which further helps in making analytical measurements. The spectrophotometer is one such good and the precise analytical optical instrument used for measuring the detections gained by biological specimens. You can check the UV spectrometer price online as well as offline medium. 

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