# Modern Physics:

Modern Physics is the name used to designate a period of development of physics in the 20th century, more specifically in the first thirty years. The term serves to differentiate the conceptions of classical physics regarding gravity and other physical entities. In this new era, nature would be studied from a different point of view, with the emergence of the theory of relativity, proposed by Albert Einstein, for example.

In the Modern Physics phase, phenomena of different orders are studied, which go beyond the limits found by the other generation of physicists. Now, it would be possible to understand physical events that happen at very high speeds, relating this to the issue of space and time.

Modern scholars wanted to understand issues so complex that they could not be explained solely with the knowledge inherited from the previous century. This was the impetus to understand several phenomena never before addressed by physics in such depth, such as the photoelectric effect. If you want to better understand these events, the theories and characteristics of Modern Physics, continue reading this article.

## Growth and development of Modern Physics

As previously mentioned, modern physicists sought solutions to complex phenomena they observed in nature. One of the starting points for Modern Physics was to understand how radiation behaved towards black bodies.

Through studies with thermal radiation, a German physicist named de Kirchhof, it was possible to observe that radiation behaves differently when it comes across a black object. In general, these bodies absorb more radiation than other colors.

This conclusion was the starting point for the growth of quantum mechanics, an essential area of ​​Modern Physics. Shortly after Robert Kirchhof, another German, called Max Planck, resolved the issue of radiation emission from black bodies.

To do this, he assumed that the electromagnetic waves emitted by that object must have an associated mathematical value. He created a standard, like small packages that could be multiple within a body.

### Planck’s Constant

Therefore, Planck’s constant (h) was created, which is worth h = 6.6260700410 -34 m 2 .kg/s. This h value can be multiplied by integers to represent the amount of radiation emitted by a given body.

Initially, the theory and values ​​were not well accepted in the scientific community, but, little by little, other physicists became interested in the knowledge brought by Planck. It was then that Einstein and Bohr also launched theories that could be related and even reinforce what had been proposed by the Germans.

Currently, Planck’s constant (h) is used to designate photons. Remember, Niels Bohr was a Danish physicist who observed an atomic model in which electronic orbits were organized around the nucleus and each shell would have a defined energy value, supporting a specific number of electrons.

Therefore, the photon appears when an electron transits between these electronic layers of the atom, in order to release energy. Note that a photon emits energy and light, but does not carry matter with it. It is the concept behind how lights work, something so important for the survival of organisms and also for the development of society as a whole.

## Important Contributions of Modern Physics

At the end of the 19th century, in the middle of the last decade, the German physicist Wilhelm Conrad Röntgen noticed the existence of a wave that had not yet been recognized at the time. They were X-rays, which have a higher electromagnetic frequency than ultraviolet waves.

This knowledge was useful, mainly due to the way this radiation relates to the different tissues and organs of the human body. It is from X-ray radiographic examinations that doctors are able to draw up treatment plans or initial investigation of any pathology, such as evaluating bone fractures, the presence of contents in the lungs, etc.

Shortly afterwards, in 1869, radioactivity was discovered, so to speak. It was the basic knowledge for the development of many of the technologies used to this day. Soon after came the most striking studies, especially by Max Planck and Bohr’s contributions appeared a few years later.

## Physical discoveries

From then on, physical discoveries were increasingly innovative compared to what was classically known. For example, at the beginning of the 20th century, Einstein proposed and proved mathematically that, if a body travels at a speed very close to the speed of light (3.10 8 m/s ) , it would have a different perception of the passage of time and space than that humans are accustomed to. It was the well-known Theory of Relativity .

Each time the ideas deepened, for example, in the 1920s a physicist called Louis De Broglie observed and described that, given the right conditions, a body can behave like a wave — this is what we call wave-particle duality.

Finally, Quantum Mechanics emerged, an area of ​​physics that studies dynamics at microscopic sizes. Quantum scholars seek to understand the movement of particles inside atoms and their subparticles, with all the interactions between them.

In this phase of scientific effervescence, other specific areas were also in constant growth. In a way, the contents intersect with each other for a more solid development of knowledge. This is the case, for example, of the discovery of radioactivity by physicists and also of radioactive elements by chemists, such as Radium and Polonium — which were described by Marie and Pierre Curie.

In fact, one of the most complete atomic models emerged in the context of Modern Physics, in accordance with what was proposed by physicists. It was the experience of Rutherford and Bohr, who proved a different atomic model, with circular orbits in which negative particles circulate, which surround a massive nucleus with neutral and positive content.

(Enem 2016 PPL) Some children, when playing hide and seek, cover their eyes with their hands, believing that, by adopting this procedure, they cannot be seen.

This child’s perception goes against scientific knowledge because, in order to be seen, objects

a) They reflect particles of light (photons), which reach the eyes.

b) They generate particles of light (photons), which reach an external source.

c) They are hit by particles of light (photons), emitted by the eyes.

d) They reflect particles of light (photons), which collide with the photons emitted by the eyes.

e) They are hit by light particles (photons), emitted by the external source and by the eyes.