This technique prevents scratching of the cuvette in those areas through which the light will pass. Scratches on the cuvette can lead to erroneous measurements.

A cuvette is, basically, a glorified test tube for use in a spectrometer. They're sometimes square in cross section to avoid refraction artifacts. Depending on what part of the spectrum is under consideration, they may be made of quartz, though plastic and glass cuvettes do exist.

You put a liquid sample into it then put the cuvette into the instrument. The beams inside of the instrument can 'see through' the quartz and 'read' your sample.

1: control, recalibirate spectrophotometer

2: photosynthesis does not occur without light

3: photosynthesis does occur with light and live chloroplasts

4: boiling chloroplasts=no photosynthesis

5. control

Cuvette

The absorption of sample at maximum wavelength will be reduced by1/2 .

Vijay Bhoir (Flamingo pharmaceuticals Ltd.Rabale Navi Mumbai ).