Light is wave or particle or both.

Theories of light:

1.      Light is an electromagnetic wave.

2.      Light is made up of streams of photons.

Electromagnetic wave: It is the type of wave which is propagated by the periodic variations of intensity of electric and magnetic field alternately.  

Photon: A photon is a type of elementary particle that is a particle inside an atom.

                              So you would have observed that both the theories about light are opposite first suggests that light has wave nature and second theory suggests that light has particle nature as photon is particle.

        Properties of waves:

1.      Waves cannot be located in space.

2.      Waves do not have momentum.

3.      Waves do not collide with each other.

  Properties of particles:

1.      Particles can be located in space.

2.      Particles have momentum and mass.

3.      Particles collide with each other.

Proofs for proving that light acts as wave

                                -by Thomas Young

                                  Double slit experiment by Thomas Young

In 1801 Thomas Young came out with his double slit experiment in which he proved wave nature of light. He believed that light has wave nature and so to put his believe in front of all he did double slit experiment in which he made two holes in a slit such that the diameter of each hole was equal to the wave length of wave. Then on one side he placed a point source of light and on other side he placed a screen. Then he observed that the bright spots were not in line of holes but were scarred this proved that light was a wave as if light would be a particle then the bright spots would be in same line that of hole. So by this experiment Thomas Young proved wave nature of light.

        Proofs for proving that light acts as particle

                                -by Albert Einstein

                                 Photoelectric effect by Albert Einstein in 1905

In the year 1905 Albert Einstein who thought that light was made up of particle showed the whole world photoelectric effect which proved that light was made of particle that is photon. He just took a metal sheet and targeted a beam of light on it. Then he observed that when photons from the light beam collide with metal sheets then photoelectron gets emitted. So these prove that light beams have momentum and particle can have momentum but waves cannot have momentum. Hence by photoelectric effect it was proved that light has particle nature.                                      

            Louis de Broglie’s concluding statement

Louis de Broglie was the hero of the whole light theory. He gave a fact that every particle in the universe emits waves. We are also made up of particle so we also emit waves but there is a fact that the thing having higher mass emits less waves so as our mass is very high as compared to mass of photons, waves emitted by us are negligible but photons emit waves.

Conclusion:

Light has dual nature that is light can be considered as wave as well as particle.