|Spectrophotometry| Class 11th| Chapter |Cell structure and function |

Spectrophotometry is a quantitative analytical technique used to measure how much light a substance absorbs or transmits as a function of its wavelength. Here's a step-by-step explanation of how it works: Light Source: Spectrophotometers start with a light source, often a broad-spectrum lamp, that emits light across a range of wavelengths, typically from ultraviolet (UV) to visible (VIS) and sometimes into the near-infrared (NIR) region. Sample Introduction: A sample solution or substance is placed in a transparent container called a cuvette. This cuvette is usually made of glass or quartz and is designed to allow light to pass through it. Monochromator: The light from the source is then passed through a monochromator, which is a device that selects a specific wavelength of light. It does this by dispersing the light into its various wavelengths and allowing only the desired wavelength to pass through. Sample Interaction: The selected wavelength of light passes through the sample in the cuvette. The sample absorbs some of the light energy at that specific wavelength, and the amount of absorption depends on the concentration and nature of the substance in the sample. Detector: The transmitted light (light that was not absorbed) is detected by a photodetector, which measures the intensity of the light. The detector converts this intensity into an electrical signal. Data Analysis: The electrical signal is then processed by a computer or spectrophotometer software, which calculates the absorbance of the sample. Absorbance (A) is a logarithmic measure of how much light was absorbed and is typically calculated using the formula: A = -log(T), where T is the transmittance (the fraction of light transmitted through the sample). Calibration: To determine the concentration of a specific substance in the sample, a calibration curve is often created. This curve relates the known concentrations of the substance to their corresponding absorbance values. By measuring the absorbance of the sample and comparing it to the calibration curve, the concentration of the substance in the sample can be determined. Spectrophotometry is widely used in various fields, such as chemistry, biochemistry, environmental science, and pharmaceuticals, for applications like quantifying the concentration of analytes, identifying substances, and monitoring chemical reactions. It provides valuable quantitative data about the interaction of light with matter. #biology #biochemwala