The kinetic energy K of the electrons is adjusted by selecting a value of the potential difference in the electron gun. Thermal electrons are released from a heated element (usually made of tungsten) in the electron gun and accelerated through a potential difference becoming a well-collimated beam of electrons produced by an electron gun. Their nickel sample was specially prepared in a high-temperature oven to change its usual polycrystalline structure to a form in which large single-crystal domains occupy the volume. In the particular experiment that provided the very first evidence of electron waves (known today as the Davisson–Germer experiment), they studied a surface of nickel. Davisson and Germer did not set up their experiment to confirm de Broglie’s hypothesis: The confirmation came as a byproduct of their routine experimental studies of metal surfaces under electron bombardment.
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Germer performed a series of electron-scattering experiments that clearly showed that electrons do behave like waves. This means that the radii are not arbitrary but must satisfy the following standing-wave condition:Įxperimental confirmation of matter waves came in 1927 when C. This produces a circular string that vibrates in normal modes, satisfying the same standing-wave condition, but the number of half-wavelengths must now be an even number and the length l is now connected to the radius of the circle. Now suppose that instead of having the string clamped at the walls, we bend its length into a circle and fasten its ends to each other. This is the condition for a standing wave on a string. If the length of the string is l ( (Figure)), the wavelengths of these vibrations cannot be arbitrary but must be such that an integer k number of half-wavelengths fit exactly on the distance l between the ends. To see it clearly, imagine a stretched guitar string that is clamped at both ends and vibrates in one of its normal modes. The physical explanation for the first Bohr quantization condition comes naturally when we assume that an electron in a hydrogen atom behaves not like a particle but like a wave. Using the concept of the electron matter wave, de Broglie provided a rationale for the quantization of the electron’s angular momentum in the hydrogen atom, which was postulated in Bohr’s quantum theory. Any particle that has energy and momentum is a de Broglie wave of frequency f and wavelength
We are recalling them now in a more general context. These new technologies drive discoveries in other sciences such as biology and chemistry.Īccording to de Broglie’s hypothesis, massless photons as well as massive particles must satisfy one common set of relations that connect the energy E with the frequency f, and the linear momentum p with the wavelength We have discussed these relations for photons in the context of Compton’s effect. Quantum mechanics has paved the way for new engineering inventions and technologies, such as the laser and magnetic resonance imaging (MRI). In 1926, De Broglie’s hypothesis, together with Bohr’s early quantum theory, led to the development of a new theory of wave quantum mechanics to describe the physics of atoms and subatomic particles. Today, this idea is known as de Broglie’s hypothesis of matter waves. In 1924, Louis de Broglie proposed a new speculative hypothesis that electrons and other particles of matter can behave like waves.
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