Production of Light

How is light produced?

Before getting into depth of production of light, let us define the term quanta or quantum.A quanta is the minimum amount of a given physical unit.It is the smallest amount of a given physical entity such as energy or matter.The quantum of light or as for that matter any electromagnetic radiation is known as a "photon".The current understanding of optics and formation of light is due to the efforts of Max Planck and Albert Einstein.

The electron in the atom acquires the energy of a photon , this energy acquired by the electron is greater than the work function of the electron in the atom.This helps in the electron overcoming the force which binds the electron to the atom , which in turn causes it to be ejected out , provided the energy possessed by these photons is greater than the work function. This results in the electron gaining kinetic energy.

With an increase in the intensity of the light rays more electrons are ejected out due to the presence of more photons. The energy acquired by the electron depends on the energy of the photon and has no relation with the light ray.

The maximum amount of kinetic energy possessed by the electron is given by -

K.max = hf-φ

Where,

K.max is the maximum kinetic energy of the electron

h is the Planck constant

f is the frequency of the incident photon

Φ is the work function

Optics:Introduction and History

What is optics?

Optics is the science which deals with the science of study of light , the properties of light , it's transmission and behaviour. optics involves the relationship of light of with matter and their interaction. It has found its use even in ophthalmology and spectrography , while rapidly finding its application in various fields.

History of Optics

The word optics has been derived from the Greek word τα ὀπτικά (ta optiká) which means the visual.It was the Greek and Indian civilizations that made great advances in optics, though the development of the first lens was by the Assyrians , which is modern day Iraq was the first to make the lens.These lenses were made of Quartz and were used as burning glasses.They were housed in the palace of Nimrud thus giving their name Nimrud Lens.Light was considered as one of the vital elements which is required for life by the Greeks.Euclid, around 300 BC compiled his book known as optics which dealt with the geometry and behaviour of light.It dealt with vision and how it is perceived.He thus put forth :

1.Lines (or visual rays) can be drawn in a straight line to the object.

2.Those lines falling upon an object form a cone.

3.Those things upon which the lines fall are seen.

4.Those things seen under a larger angle appear larger.

5.Those things seen by a higher ray, appear higher.

6.Right and left rays appear right and left.

7.Things seen within several angles appear clearer.

Even the Hero of Alexandria in his famous catoptrics has dealt with various factors of optics.While in the Islamic countries, al-kindi and Ibn stahl put forth a number of axioms related to optics.