On the last page we saw that light has a dual nature. It is both a wave and a particle. Though such characteristics surely seems strange a French scientist Louis De Broglie created the even stranger theory in 1924. He came to the opinion that if light could be sometimes described as a wave then maybe matter could be sometimes conceived as a wave.
He suggested that there was a wave connected with a moving particle. The length of that wave, as he said, is equal to:
The formula shows that a particle of smaller velocity and smaller mass is characterised by the longer wavelength. Let's imagine two examples:
1) A baseball of a mass of 0,14 kg is thrown with a 40 m/s velocity by a pitcher. After placing the data to the formula we get a 1,2*10-34 m wavelength. It isn't much, actually even using the most modern technologies you wouldn't see it.
2) On the other hand an electron moving with a 40 m/s velocity has a 1,8*10-5 m wavelength. Such waves can be observed.
The de Broglie theory was experimentally confirmed in 1926 and 1927. It was done independently by two scientists. They were Clinton Joseph Davisson and George Paget Thomson (the son of the discoverer of electron).
Clinton Joseph Davisson and Laster Germer shot the crystal of nickel with a beam of electrons. That caused a secondary emission of electrons from the crystal. The number of electrons sent in different directions was defined by using the collector - a metal plate, which collected the falling electrons. The collector could have been moved around the crystal. By the accident one of the nickel plates got oxidised. To remove nickelic peroxide the plate was heated. After that the plate was used again in the experiment. But the results occurred to be completely different than before. That was because the method of cleaning the plate turned it into a big monocrystal. The electrons were emitted from such plate in all directions but at some angles the emission was bigger. If the electrons really had the dual nature, they would undergo diffraction, just like light. And indeed, this, what Davisson and Germer observed, was the diffraction of the electrons.
At the same time George Paget Thomson (J.J. Thomson's son) conducted a different experiment and also proved the wave structure of the electrons. He was bombarding thin (about 10-5 cm) gold foil by a beam of electrons having high velocity. While the electrons were going through the foil, the diffraction occurred. Thomson observed the diffraction rings on the screen behind the foil.
The two described above experiments were the most important ones confirming the wave nature of the electron. But anyway there were more such experiments conducted. And de Broglie's hypothesis was fully confirmed.
So with matter it is similar as it was with light: matter also has dual, wave - particle nature. In no experiment we see both characteristics at the same time. Sometimes matter acts like a wave and some other times like a particle. To understand what matter is one must take its both characteristics into consideration. Neither the theory of particles nor the wave theory of matter are correct if considered alone. Only combining these two, one gets a full and proper one.
Thomson's and Rutherford's different ideas of the atom