Qualitative ideas of black body radiation

To study the qualitative ideas of black body radiation, you must know that the ideal black body notion is of chief importance in the theory of thermal radiation and electromagnetic radiation, where energy is transferred togetherly with wavelength bands. 

Definition of a Black Body

A black body can be defined as allowing the incident radiation to pass through itself without any energy reflection. It steadily absorbs radiation inside itself without giving in to any other. This property has validity in every type of radiation of wavelengths and angles of incidence.

Black bodies are ideal radiation absorbents and have many other properties that hold an important place in physics. 

Some essential characteristics of these black body radiation are as follows:

1. A black body emits radiation of all wavelengths in ultraviolet, visible, and infrared. 
2. With the increase in temperature of the black body, the overall amount of radiation emitted also increases. 
3. The energy distribution isn’t uniform. At a wavelength of λm, the energy emitted is maximum. 
4. The wavelength λm decreases when that energy emitted is maximum, and higher temperature.

Laws of Black Body Radiation:

Considering the general law of thermodynamics, many scientists proposed different laws on black body radiations. The laws of black body radiation are as follows-

1. The Wien radiation law
2. The Planck law
3. The Wein displacement law
4. The Kirchhoff law
5. The Stefan Boltzmann law
6. The Rayleigh-Jeans radiation law

Absorption Of Radiation by Black Body

The radiation absorbed from a heated body depends on the body itself. To visualize this, let us consider how different materials can absorb radiation. You can observe that radiation absorption doesn’t happen. This situation arises in the case of ordinary glass, as no frequencies correspond to light.

STEFAN-BOLTZMAN LAW

According to this law, the emission of radiant heat energy is directly proportional to the fourth power of its ideal temperature. It was Formulated in 1879 by an Austrian physicist named Josef Stefan after his experiment. An equivalent law was also derived in 1884 by a physicist named Boltzmann from his thermodynamic considerations. According to him, if E is the radiant heat emitted from a unit area in one second and T be the temperature (in kelvins), 

then, E = σT4

 The Greek letter sigma (σ) stands for the proportionality constant, also called the Stefan-Boltzmann constant. Stefan Boltzmann’s constant value is 5.670374419 × 10−8 watt per meter 2 per K4. This law applies only to black bodies that absorb all incident heat radiation.

Stefan- Boltzman law formula:

Stefan Boltzmann’s law deals with the temperature of the black body to the quantity of power it emits in per unit area. One can obtain the overall power that gets radiated on the wavelength of a black body by integrating Plank’s radiation formula. 

Before examining the theory of thermal radiation, one should study the model of a perfect black body. As we know, it is a type of body that absorbs all falling radiation. The foremost simple yet successful, maybe a model representing an almost completely closed cavity with a tiny low aperture. The light beams inside the insulated cavity lose their intensity after corresponding reflections get captivated there. This happens so as the heated walls of the cavity are sources of thermal radiation, and only an insignificant part of it leaves it. There exists an ideal equilibrium density of radiation within the cavity. Standing waves are produced within the cavity. As for standing waves during a string, the utmost wavelength of undulation is decided by the dimensions of the cavity. Also, the minimum wavelength is set by the discrete character of the substance from which the walls are made. Thus, it can be said that the density of standing waves is finite in the insulated cavity. After detailed consideration, one can obtain ω2/4π2c2.

Conclusion:

Applications Of Black Body Radiation:

Black body radiation is applicable in many ways in our lives. Some of the applications of these radiations are mentioned below-

1. Radiation and radioactive substances are often utilized in the medical field for diagnosis, treatment, and research. For instance, X-rays. Radiotherapy is additionally used for cancer treatment.
2. Electromagnetic radiation is used in most modern kinds of communication systems.
3. Radioactive atoms are accustomed to determining the age of materials within the process of radiocarbon dating.
4. Radiation is additionally utilized in determining the composition of materials. This process is termed neutron activation analysis.

On the opposite hand, radiation also has harmful effects on living beings. They will cause burns or, in severe cases, cancer or genetic damages. Radioactive waves are carcinogenic to humans.