How important is the light for us? What is the light? As always, we can look at the issue from many different perspectives, and in this article we will investigate the topic from the scientific one. In the following articles, we will talk about the cultural and spiritual perspective. What is light in physics?
Light is the smallest energy that can be transported. A photon is a fundamental particle of light that cannot be broken down, but only destroyed or created. Light has a wave-particle nature, so it has both wave and particle characteristics.
Light is energy that travels in the form of an electromagnetic wave. It is the same phenomenon as the waves in the ocean. When we colloquially say "light", we most often mean "visible light" (seeing colors), i.e. a spectrum of light with a specific frequency that is perceived by the human eye. It is worth emphasizing here that this is only a small section of the electromagnetic spectrum, so we may assume that there are tons of colors that are not visible to humans, or that each being may perceive different parts of the electromagnetic spectrum in different, not just visual, ways. The spectrum mentioned above ranges from gamma rays, through X-rays, ultraviolet, visible light (colors), infrared, radio waves and many other waves. All these waves belong to one spectrum but of different frequency. All these waves are waves of light.
High frequency waves have the highest energy but are the shortest. An example of such a wave is gamma radiation, which has so much energy that it can cause changes within the DNA at a relatively fast pace. Therefore, each energy wave is able to change our DNA, but at a different time of exposure. The longer the waves are, the lower their frequency and the less energy they have. Please, look at the drawing under THIS LINK now. It explains the relationship I have presented. Each color (visible light) has a different frequency, wavelength, and therefore a different amount of energy. The higher the frequency, the shorter the wavelength and the greater the energy it carries. With more energy, it is easier to change something at the cellular, genetic, molecular or atomic level! It is also worth remembering that light travels in a vacuum space at a speed of 3 million meters per second (300,000 kilometers per second = 3 billion kilometers per hour).
Where does light actually come from? Most of the light comes from emissions that result from the dropping of an atom from a higher to a lower energy state. It happens when an electron in an atomic shell changes its position to a higher or lower energy level. When the electron drops to a lower energy level, the energy drops and the lost energy is emitted in the form of an electromagnetic wave. When is this happening? When we heat or burn something, molecules are oxidized, which leads to the emission of heat and light. Atoms descend to lower energy levels, and that is why the product of combustion cannot serve as a re-combustion facility that is equally high-energy and equally efficient. It may happen that the opposite situation occurs, when the light reaching the atom raises its energy to the excited state. In such a situation, the electron absorbs the energy of this wave and enters a higher energy level, and the atom passes to the so-called Excited form. Energy in nature circulates and what is lost in one place will raise the energy in another.
Matter influences light by absorbing some or all of its energy, therefore, for example, the Earth's atmosphere scatters light waves of different colors depending on the angles of incidence of light rays, giving us a visual impression of specific colors. The sky is blue during the day and red or pink in the morning. Light has another surprising ability - its waves can stretch and decrease in frequency due to the expansion of the Universe. The light waves that reach us from distant stars stretch over time, causing the once-red star to gradually fade into infrared invisible to the eye. However, remember that not everything in the universe emits light - there is a huge amount of dark energy and dark matter that do not emit any light rays, even those invisible to the human eye!
The last question that arises is why organisms on Earth have developed eyes that are primarily focused on seeing this particular part of the electromagnetic spectrum (colors), rather than registering the spectrum of electromagnetic waves outside of this range? Well, it is this range that has a good water penetration rate, in which the first organisms on Earth that had eyes evolved. The purpose of "inventing" the eyes was to create a method of collecting information from the environment that would take into account the registration of the interaction of matter with light (with electromagnetic waves). What's going on here? What exactly is color vision? When we see a yellow flower, we actually receive information that the flower absorbed different parts of the electromagnetic wave spectrum, but reflected some of the waves, recorded as yellow. On this basis, organisms could create a relationship with this color and make predictions about the level of safety of interactions with the world around them, e.g. the red color of blood can give a sense of danger, but only for organisms with such a blood color.
Let the light guide you in the dark