What is this thing called light ?

 As in our early study, we can say " A light is the form of energy which gives sensation of sight in our eyes" and also we had done card hole experiment to proved that light can travel in a straight line or path.

                  we ordinarily live surrounded by light- sunlight, electric light, candle light etc. are all sources of light. We would not be able to see a thing without light, and a life without light is something that we cannot even imagine.

                  something so familiar should have been the begining of qauntum mechanics, must be surprising to many people. For one thing since we know that quanta are invisible, but we know "light is visible,"and also we cannot answer the questions such as ,

                 What is the shape of light ?

                 How is light perceived by our eyes ?

In fact no one has seen the actual form of light. It is weird that, we see it and yet we dont see it. Then how was it explained by physicist ? sounds interesting.

       Before quantum mechanics was established, classical physics in the 19th century explained light as a wave. they thought this because light interferes, an eg. of interference that is familiar to everyone is collision of two waves on the surface of water. Light itself cannot be directly observed.Nevertheless, by performing certain experiments, it is possible to observe signs that light is interfering. this was confirmed by slit experiment, in 1807 an English physicist named Thomas Young performed the slit experiment.

           But  A.Einstein proposed that light was not a continous wave , but consisted of localized particles. Now that the dual nature of light as " both a particle and a wave " has been proved, its essential theory was further evolved from electromagnetics into quantum mechanics.

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