The famous Davisson Germer electron diffraction experiment was performed due to the lack of explanation of an atomic model's wave nature's properties. In 1927 scientists C.J. Davisson and L.H. Germer carried out an experiment to explain an electron's wave nature. This was proposed through electron diffraction method.
This section discusses the experiment and its observation in a detailed manner. The explanations are lucid in nature to help students understand the concepts better. This topic carries heavy weightage in term of marks in the examination.
With a thorough reading, students can solve the variables and equations related to Davisson Germer experiment easily.
Under the Davisson Germer electron diffraction experiment, a student can get the value of scattering angle θ. They can also find the possible difference V's equivalent value at which electrons' scattering is the highest. The data collected by Davisson and Germer gives two theories or an equation that again shows the same value for λ. If we include De Broglie's duality in a wave-particle, there can be two equations (a) and (b).
The equation that substantiates the De Broglie's wave-particle duality is –
λ = h/√2meV2meV
Here one can find V's value to be 54 V
Now we know that λ = 12.27/√5454 which gives us the value 0.167 nm
If we go through the equation, we find that'd' will have a value of 0.092 nm. It is gained through X-ray scattering. That gives us v's value to be 54 V. The angle of scattering is equal to 500500.
Now applying this value in a second equation, we get that
(b) nλ = 2 (0.092 nm) sin( 900−500/2)900−500/2)
Let's take n's value to be 1, while λ is 0.165 nm
This value finally verifies the theoretical explanation of the De Broglie equation.
To find the presence of an electron in a particle form, a student can use a detector. Davisson Germer electron diffraction experiment indicates that a detector receives electronic current, i.e. electron. Here the strength or intensity of an electric current produced or received and scattered in an angle is studied. This current referred to as electron intensity.
Another observation that students can find here explains how the intensity of a scattered electron is never continuous. One can find both minimum and maximum value analogous to the utmost and least diffraction pattern gained via X-rays.
Scattered electrons have continuous intensity levels, which displays a maximum and the least analogous value to the utmost, and minimum value of a diffraction pattern created by X-rays. This value can be found by studying potential differences and scattering angles.
Lastly, under this Davisson Germer electron diffraction experiment, a student can understand the setup formed. Ideally, the thought behind this elaborate experiment was the nature of wave particles reflected.
Davisson and Germer's experiment shows that waves reflected in a Ni crystal that passes two atomic layers contain a constant phase disparity. Students can learn that after reflection, these waves encumber annihilation or construction. This gives rise to the famous diffraction pattern.
It is seen that during the Davisson and Germer experiment, electrons are replaced with wave particles. These electrons combined to form a diffraction pattern. Finally, producing the ultimate result, which is the dual nature of matter.
Davisson Germer experiment electron diffraction chapter is complicated in terms of equation and usage. A student needs to have a clear understanding of the basic topics that carry high marks. This complex topic requires students to depend on guidebooks and study materials that offer only exercises not a valid explanation.
Q1. What Do You Understand by Einstein's Photoelectric Equation in an Energy Quantum of Radiation?
Ans. Albert Einstein in 1905 projected a fundamental picture of quanta of radiation or electromagnetic radiation that defines the photoelectric effect. Under this proposal, each radiant energy has energy hv. Here h falls under planks constant and frequency of light shown as v.
Ideally, under the photoelectric effect, the quantum of energy of radiation or ‘hv’ is absorbed by an electron. If this absorbed quantum of energy surpasses from the defined minimum energy required for the escape of electron from the metal surface, then an electron with maximum kinetic energy will be
Kmax = h v ‒ ϕ0
Here, the value of a selective material's work function will be constant as it depends on a material's nature.
Q2. What Does the Wave Nature of Matter Mean?
Ans. Ideally, the wave nature of light can be shown as a phenomenon related to interference, polarization and diffraction. While one can find in a photoelectric effect and Compton effect, radiation acts as photons, also known as a bunch of particles. Here the momentum transfer also gets effected, which changes with a photon.
If radiation contains dual wave-particle, then whether a particle of nature exhibits the wave character or not, De Broglie answered this in his hypothesis. He attributes a matter with a wave-like character. If a dual nature is seen in terms of radiation, then the matter will show similar character.
According to De Broglie, a wavelength λ is linked with momentum particle or p. This gives us λ = h/p = h/(m v). Here m represents a particle's mass and speed is shown as v.
Q3. What is the Purpose of a Photoelectric Cell?
Ans. A photoelectric cell usually has a technical application. It is a device that gets affected by lights due to its electrical properties. It also converts a light's energy into electricity directly via a photovoltaic effect. This is ideally a chemical and physical phenomenon. Here, the electrical characteristics, including voltage, current or resistance, show different features when it comes in contact with light.
Also termed as an electric eye, a photocell is used in producing sound in motion films. They are also used for scanning and telecasting scenes from a television camera. Some industries use this device to detect minute holes in the metal sheet needed for construction.