Carnot’s theorem was developed by Nicolas Léonard Sadi Carnot while researching on the efficiency of the heat engine.

Carnot Cycle is a theoretical thermodynamic cycle proposed in 1824 by a French physicist Sadi Carnot. It explains the maximum limit of the thermodynamic engine that can be achieved while converting heat to work or conversely, the efficiency of a refrigeration system in creating a temperature difference by the application of work to the system.

Any system following the reversible Carnot cycle is known as the Carnot heat engine and is a theoretical engine.

Generally, a heat engine operates by transferring energy from a warm region to a cool region of space. In the process, energy is converted to mechanical work. This cycle can be reversed too.

Carnot’s Theorem is derived from the 2nd law of thermodynamics, it states that

  • Heat engines that are working between 2 heat reservoirs are comparatively less efficient than the Carnot heat engine that is operating between the same reservoirs.
  • Irrespective of the work details, every Carnot engine is efficient between 2 heat reservoirs.

According to the Carnot theorem, the reversible engine will perpetually have higher efficiency in performance compared to the irreversible engine. The reversible heat engine works on a reverse cycle and functions as a heat pump (or refrigerator).

The efficiency of the heat engine is found by:


the ratio of work done by the heat engine

TC is the absolute temperature of the cold reservoir

TH is the absolute temperature of the hot reservoir

Let’s learn about another important concept of Physics – the Raman Scattering

Why The Sky Is Blue??

Due to the scattering effect, light from the massive source – the sun is distributed to the entire earth. Let us find out in detail what is the medium of transmission of scattered light and what the phenomena is known as.

Raman Scattering is a phenomenon in which explains the process of scattering in the light. In 1928, Sir C V Raman explained that “there is an inelastic scattering of photons from the molecules such that they are excited to higher levels known as Raman scattering which is also known as Raman effect”.

Scattered photons in the Raman effect usually have energies lower than that of the incident photons. Raman spectroscopy is a device designed and developed based on Raman scattering and is used to study the materials by chemists and physicists. Raman spectroscopy is combined with Microscope and is developed as Micro Raman Spectroscopy.

When the light comes in contact with molecules in the air, the predominant mode of scattering is known as elastic scattering which is also known as Rayleigh scattering. Rayleigh scattering is responsible for the blue color of the sky; it increases with the fourth power of the frequency and is more effective at short wavelengths.

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