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Max Planck studied the electromagnetic wave characteristics and put forward certain definite postulates. These suggestions were insightful in further scientific analysis of phenomena like diffraction, interference, etc. Though his efforts were very commendable and he even received the Nobel Prize in the field of Physics, still his theories could not prove many processes. Some of them are the photoelectric effect, line spectra of atomic hydrogen, the phenomenon of radiation when bodies are subjected to thermal stimulus, etc.
Radiation of blackbody
Before grabbing an idea about Planck’s Quantum Theory, it is essential to know about the concept of a blackbody. When heat is increased above a certain limit, solid objects tend to discharge radiation which fluctuates within a wavelength range. This can be understood with a real-life example. When we apply heat to a solid substance, its color transforms as we keep on expanding the thermal exposure. This color transformation takes place due to varying ranges of wavelength – from low to high. In the majority of the cases, we notice metals glowing in blue color after it has already gleamed in red. This phenomenon occurs when we apply more heat to the metal. In Physics, a black body is described as an ideal object that is capable of absorbing and emitting all frequencies. The radial energy released from such objects is termed black body radiation.
The phenomenon of blackbody radiation is therefore entirely dependent on temperature. The radial energy intensifies if there is an enhancement in the wavelength λ. This proposition has been proved through Planck’s Quantum Theory. However, this radiation increases to a limit after which there is an inevitable decrease if the wavelength λ is increased. Maxwell could not explain this concept. Hence, Max Planck came up with his quantum theory to scientifically describe the situation.
Planck’s Law
In Physics, the power spectrum of waves with electromagnetic energy that are discharged by a blackbody in an environment of thermal equilibrium is described by Planck’s Law. The temperature is considered as a constant T. Also, the flow of energy between the two involved systems must be null as per the law.
In classical mechanics, an object is described as an accumulation of matter that remains surrounded by a contiguous boundary. Every such object constantly releases electromagnetic radiation. The radiance flux of an object O explains the emissive spectral strength for unit angle and area. This applies to certain frequencies of radiation. Planck’s law gives us the relationship between the temperature and the spectrum wavelengths. We notice a rise in the spectrum emission with an increase in applied temperature.
Planck’s explanation of black body radiation: O (T, v) = 2 v3h/c2x (1 ÷ ehv/kbT– 1)
In the above equation, the frequency of the radial object is given as v. The temperature here is considered to be so temperature T. The Planck’s constant is represented by h. Boltzmann constant is conventionally denoted by kb while c is the velocity of light.
Planck’s Quantum Theory
The following postulates have been put forward in Planck’s quantum theory:
- The molecules and atoms of different elements both absorb and release energy or work as free units. The minimum quantity of radial energy that is possible to be absorbed or released as electromagnetic waves is described as quantum.
- The radial energy’s frequency (v) shares a directly proportional relationship with the emitted or absorbed energy quantity.
The mathematical representation of the proposition is given as:
E = h v. Here the radiation energy is signified as E. Already we have discussed in the article that h is Planck’s constant that has a definite value (6.626 x 10-34 Joules seconds). While v stands for the frequency of emitted or absorbed radiation in Planck’s Equation.
Planck’s Equation: E = v. h
The above-mentioned relation only explains the emission and absorption of electromagnetic radiation. This mathematical expression shows zero effectiveness in explaining the physical phenomenon of radiation. In 1905, celebrated Physicist Sir Albert Einstein further nurtured Planck’s quantum theory to summarize the photoelectric effect. The photoelectric effect is the phenomenon of emission of electrons from the metal surface when that surface is exposed to any incident light. Here, the photon particles dislodge the electrons from the valence shell of the constituent metallic atoms once the activation energy is exceeded. Einstein identified photons as the particles of incident light beam with the help of Planck’s theory.
Conclusion
Planck’s quantum theory is a fundamental concept of quantum mechanics. We identify the quantum characteristics of electromagnetic radiation with the help of his theory. Also, it becomes possible to classify various electromagnetic waves based on frequency and wavelength. Planck’s Law states that energy is never radiated in fraction but in whole such as hv, 2hv… 4hv, and so forth.
