User:Nagham ashraf/sandbox

Spectrophotometer is a device used to measure the concentration of unknown substance in a solution by measure the light intensity Pssing through it the substance or by the amount of absorption by a specific substance.

Spectrophotometer consist of :

1)Source of light

2)A way to focus light in the sample (wavelength selector )

3)Monochromator to separate the light into it’s component (wavelength).

4)Detector to measure the intensity of light at each wave length or amount of light absorbed by specific substance

Soectophotometer are employed in many different fields and found in both scientific laboratories and production facilities

The spectrophotometer act on two principle :

1) The darker solution will absorbed more than the lighter one ,because dark substance have more number of molecules than the lighter solution ,so the absorbed will be more

2) The light energy absorbed and transmitted must be equivelent the energy required

The development of a computer-controlled spectrophotometer that enables measurement of spectral transmittance, reflectance, and optical loss of thin-film specimens is discussed. We also describe the design and testing procedure of the spectrophotometer, incorporating test sample performance data. In the visible region the overall photometric accuracy is verified to be 0.1% and 0.2% for transmittance and reflectance, respectively. The wavelength scale is accurate to within 0.5 nm with a reproducibility of 0.1 nm.

How does a Spectrophotometer Work?

The spectrophotometer is an optical instrument for measuring the intensity of light relative to wavelength. Electromagnetic energy, collected from the sample, enters the device through the aperture (yellow line) and is separated into its component wavelengths by the holographic grating. Simply put, the grating acts to separate each color from the white light. The separated light is then focused onto a CCD array detector where the intensity of each wavelength (or each color if in the visible region) is then measured by a pixel of the array. The CCD is then read-off to a computer and the result is a spectrum which displays the intensity of each wavelength of light.