What is Lambert -beer law?

Answer 1

Beer's Law, also known as the Beer-Lambert law, relates the attenuation, or reduction, of light to the properties of the material it passes through. It's mainly related to the BGK model, which is a mathematical model that helps describe collisions of particles.

Answer 2

The modified Beer-Lambert law is central to the operation of functional near-infrared spectroscopy (NIRS). It describes the amount of light passing through the head. To get to an understanding of this law, however, we will build up from simpler laws and discoveries.

Light is made up of photons. Photons are very special because they act in two very different ways at the same time - as a particle and as a wave. Water can also be thought of as being like this. A drop of rain and a ripple in a lake are made of the same thing - water. Photons of light are little packets of energy smaller than atoms and, since they are waves, that must mean they have a wavelength (which is really just the length of the wave from peak to peak). The light that we see has very small wavelengths. Violet photons of light have the shortest wavelength - only 380 nanometres long (380 millionths of a metre) and red photons of light have the longest wavelength - but are still only 750 nanometres long.

As photons of light move through space, they will come in contact with atoms. If a photon comes in contact with an atom, one of two things will happen: Either the photon will collidewith the atom and bounce off it or the atom will absorb the photon. A photon can only be absorbed by an atom is the photon has the right wavelength.