Define Single Beam and Double Beam Optical Path?
In simpler instruments, a single beam of light passes through the cuvettes and reaches the detector whereas in the double beam systems, to compensate for the possible variation in the intensity of the light source, the light beam is split from the lamp. One portion is directed to the reference cuvettes and the other to the sample cuvettes. Any change in light intensity, affects both the cuvettes simultaneously and thus is cancelled out.