Single beam filter photometer

Single beam filter photometer:

Diagram:

single beam filter photometer
single beam filter photometer

Theory:

It consists of a source of light (tungsten filament lamp), lens to make the light beam parallel, filter of wavelength selection, cuvette with sample holder for keeping the solution to be analyzed , detector (photocell) and reading device (galvanometer or micro-ammeter).

The tungsten filament lamp gives the light radiation. This light is incident on the lens which makes it a parallel beam of light. This parallel beam of light is passed through the sample solution after passing through a filter. The sample absorbs some light energy, transmitting the other. This transmitted light falls on the photocell that generates the photocurrent. This photo-current is recorded by the galvanometer or micro ammeter which is having transmittance scale, since the photometer is directly proportional to the transmitted light, the transmittance scale is linear.

Steps in experiment:

1)      With photocell darkened, the meter is adjusted to zero by zero adjustment.

2)      The blank or reference solution is inserted in the path of light beam and light intensity is adjusted by means of rheostat in series with lamp. With this adjustment the meter reading is brought to 100 scale divisions.

3)      Solutions of both standard and unknown samples are inserted in place of blank and the reading of the specimen relative to the blank is recorded.

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