Optics

I assume you already have basic knowledge of optics. Optics is the study of light. Optics describes how light is created and how it travels. An important part of optics is the study of what happens when light hits different surfaces. When light hits a surface, it may be reflected, refracted, or absorbed.

• Reflection occurs when light hits a surface and bounces back. Reflected light makes images appear in mirrors and in other smooth, shiny surfaces.
• Refraction happens when light changes direction, or bends, when it moves from one material to another. For example, light traveling through the air refracts when it hits water. This can make a straw in a glass of water look bent at the surface of the water.
• Some surfaces absorb, or take in, light. This causes the surface to heat up. For example, a sidewalk heats up on a hot, sunny day because it is absorbing light.

Spectrophotometry

Spectrophotometry is the quantitative measurement of the interaction of ultraviolet (UV), visible, and infrared (IR) radiation with a material and has an impact on a wide field of science and technology.  Spectrophotometry uses photometers, known as spectrophotometers, that can measure the intensity of a light beam at different wavelengths. 

Types of spectrophotometers:

• Infrared spectrum: study and identification of chemical substances
• Ultraviolet spectrum: identification of molecules, black light.
• NMR spectrophotometer: atomic/nuclear absorption.
• Reflectance spectrophotometer: this is the spectrum used in paint and body shops to measure color (konica minolta, etc.)
• Double beam spectrophotometer.
• Single beam spectrophotometer.

A double-beam spectrophotometer compares the light intensity between two light paths, one path containing a reference sample and the other the test sample. A single-beam spectrophotometer measures the relative light intensity of the beam before and after a test sample is inserted. Although comparison measurements from double-beam instruments are easier and more stable, single-beam instruments can have a larger dynamic range and are optically simpler and more compact. Additionally, some specialized instruments, such as spectrophotometers built onto microscopes or telescopes, are single-beam instruments due to practicality.