2006-11-21 02:13:42 · 7 answers · asked by Anonymous in Science & Mathematics ➔ Botany
A spectrophotometer consists of two instruments, namely a spectrometer for producing light of any selected color (wavelength), and a photometer for measuring the intensity of light. The instruments are arranged so that liquid in a cuvette can be placed between the spectrometer beam and the photometer. The amount of light passing through the tube is measured by the photometer. The photometer delivers a voltage signal to a display device, normally a galvanometer. The signal changes as the amount of light absorbed by the liquid changes.
If development of color is linked to the concentration of a substance in solution then that concentration can be measured by determining the extent of absorption of light at the appropriate wavelength. For example hemoglobin appears red because the hemoglobin absorbs blue and green light rays much more effectively than red. The degree of absorbance of blue or green light is proportional to the concentration of hemoglobin.
When monochromatic light (light of a specific wavelength) passes through a solution there is usually a quantitative relationship (Beer's law) between the solute concentration and the intensity of the transmitted light, that is,
where I sub 0 is the intensity of transmitted light using the pure solvent, I is the intensity of the transmitted light when the colored compound is added, c is concentration of the colored compound, l is the distance the light passes through the solution, and k is a constant.
A spectrophotometer or colorimeter makes use of the transmission of light through a solution to determine the concentration of a solute within the solution. A spectrophtometer differs from a colorimeter in the manner in which light is separated into its component wavelengths. A spectrophotometer uses a prism to separate light and a colorimeter uses filters.
used,
1. to know the purity of DNA extracted
2. to measure the growth of bacterial cultures
2006-11-21 03:43:22 · answer #1 · answered by Lalitha 2 · 0⤊ 0⤋
Lallitha's answer contains a serious error.
The spectrophotometer cannot be used to measure bacterial growth as this causes turbidity! This turbidity blocks the path of the light so different concentrations cannot be measured.
The spectrophotometer measures the concentration of light at the different wavelengths. Where a chemical or compound absorbs the light the concentration transmitted is reduced. This can be clearly seen using its cousin the spectrometer which shows the absorption bands.
To measure the exact wavelength, the Hartley revision spectrometer is used. The 2 spectra are viewed above each other with the upper spectrum laterally reverted (the red is on the left instead of the right). The spectra are then moved until a single band passes through BOTH spectrum and the wavelength read from the Angstrom scale.
2006-11-21 08:04:18 · answer #2 · answered by beech7wood2000 3 · 1⤊ 0⤋
A spectrophotometer is an instrument that measures intensity and wavelength of light. Spectrophotometers that can detect light in the uv spectrum can be used to quantify nucleic acid, a useful tool to biotechnoligists.
2016-05-22 06:30:32 · answer #3 · answered by Anonymous · 0⤊ 0⤋
It measures the amount of light absorbed (at a given wavelength) by a sample. If the light is monochromatic it will obey Beer-lamberts law and the light absorbance can be related to the concentration of the absorbing species in solution.
Spectrophotometer usually only covers visible light. A spectrometer covers all the electromagnetic spectrum.
2006-11-21 02:29:43 · answer #4 · answered by deflagrated 4 · 0⤊ 0⤋
It is possible to measure bacterial growth this way, I just did it about five minutes ago. Yes they block the light, that's how you measure how many there are, by how much light is blocked/gets through.
2006-11-24 10:07:12 · answer #5 · answered by cheetara_2001 2 · 0⤊ 0⤋
it has alot...
one such is to measure the absorption of colours i think.....
in fact...
in an experiment i did today i had to measure the absorbance of different solns of fe3+....
using a comparitive detail,
one can measure the concentration of fe3+ provided we hav a known soln...
2006-11-21 02:28:20 · answer #6 · answered by sriraam h 2 · 0⤊ 0⤋
sure you dont mean spectrometer?
2006-11-21 02:18:37 · answer #7 · answered by adam r 3 · 0⤊ 1⤋