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Quantum theory is a branch of physics that describes how the universe functions in the smallest sizes. When things are extremely tiny, the ordinary principles of physics, from Newton’s equations to thermal physics, are useless. They are no longer functional. It assists us in explaining a variety of topics. Depending on the situation, light acts as a particle or a wave, and quantum theory can help us understand why. Quantum theory can also explain the behaviour of elements in the periodic table.
Blackbody Radiation and Planck’s Equation:
Max Planck’s theory that energy, like matter, is discontinuous was one of the first ideas offered to distinguish quantum mechanics from classical physics. This ground-breaking concept was inspired by blackbody radiation. A blackbody is an item that absorbs all of the radiation that it comes into contact with. When heated to a certain degree, an object that absorbs all radiation may also perfectly release all radiation, hence a blackbody will radiate the most energy. This energy emitted was supposed to be unlimited in classical physics. When it didn’t emit energy eternally, however, experts were stumped as to how to explain the event. As a result, Planck suggested that quantum theory, unlike conventional physics, confines energy to a set of specified values. Each of these values isn’t continuous; instead, it jumps from one permissible value to the next in a short, quantum leap. A quantum is a difference between two permissible values in a set, to be more precise.
Planck devised a model known as Planck’s equation based on the premise that all atoms on the surface of a heated object vibrate at the same frequency. Planck was able to produce a constant, Planck’s constant, using frequency and temperature measurements.
He was able to rephrase his argument using this constant: energy was exactly proportional to frequency. He structured his equation as follows:
Scientists, including Planck, were suspicious about the emerging subject of quantum theory due to a lack of strong proof. Planck’s idea was initially rejected since it could not be applied to anything other than blackbody radiation. However, it was eventually accepted once it was successfully applied to other phenomena.
Photoelectric Effect:
The photoelectric effect is based on the premise that when light is placed on a sample under particular conditions, electrons are expelled from that material. Experiments revealed that for electrons to be released, the frequency of the light must be over a particular threshold value. Scientists made three observations after researching the photoelectric effect under various settings.
For electrons to be released, they must have a particular minimum frequency.
Frequency is directly related to kinetic energy.
The intensity had no effect on the number of electrons released from the surface.
The photoelectric effect was crucial because the association between radiation and a particle of matter led scientists to realise that the wave theory of radiation would not be sufficient to describe many occurrences. As a result, wave-particle duality emerged as a new way of thinking.
The atom’s quantum mechanical model (Key Points):
Louis de Broglie proposed that all particles could be treated as matter waves with a wavelength λ, given by the following equation:
λ=h ⁄ mv
- Erwin Schrödinger proposed the quantum mechanical model of the atom, which treats electrons as matter waves.
- Schrödinger’s equation Hψ=Eψ can be solved to yield a series of wave function ψ , each of which is associated with an electron binding energy ,E .
- The square of the wave function ψ², , represents the probability of finding an electron in a given region within the atom.
- An atomic orbital is defined as the region within an atom that encloses where the electron is likely to be of the time.
- The Heisenberg uncertainty principle states that we can’t know both the energy and position of an electron. Therefore, as we learn more about the electron’s position, we know less about its energy, and vice versa.
- Electrons have an intrinsic property called spin, and an electron can have one of two possible spin values: spin-up or spin-down.
- Any two electrons occupying the same orbital must have opposite spins.
Conclusion:
Quantum theory is the theoretical foundation of modern physics, explaining the nature and behaviour of matter and energy at the atomic and subatomic levels. Natural science and natural philosophy are frequently used to describe the character and behaviour of matter and energy at that level.
