LIGHT ENERGY: CHARACTERISTICS, TYPES, OBTAINING, EXAMPLES - SCIENCE - 2024

The light energy or light is the light that carries an electromagnetic wave. It is the energy that makes the world around us visible and its main source is the Sun, forming part of the electromagnetic spectrum, along with other forms of non-visible radiation.

Electromagnetic waves establish interaction with matter and are capable of producing various effects according to the energy they carry. Thus, light not only allows objects to be seen, but also generates changes in matter.

Figure 1. The Sun is the main source of light energy on Earth. Source: Pixabay.

Characteristics of light energy

Among the main characteristics of light energy are:

-It has a dual nature: at the macroscopic level light behaves like a wave, but at the microscopic level it exhibits particle properties.

-It is transported by packages or "quanta" of light called photons. Photons lack mass and electric charge, but they can interact with other particles such as atoms, molecules or electrons and transfer momentum to them.

-It does not require a material medium to spread. You can do it in a vacuum at the speed of light: c = 3 × 10 ⁸ m / s.

-The light energy depends on the frequency of the wave. If we denote the energy and f as the frequency as E, the light energy is given by E = hf where h is Planck's constant, whose value is 6.625 10 ^–34 J • s. The higher the frequency, the more energy.

-Like other types of energy, it is measured in Joules (J) in the International System of Units SI.

-The wavelengths of visible light are between 400 and 700 nanometers. 1 nanometer, abbreviated as nm, equals 1 x 10 ^-9 m.

-Frequency and wavelength λ are related by c = λ.f, therefore E = hc / λ.

Types of light energy

Light energy can be classified according to its source in:

-Natural

-Artificial

Figure 2. The visible light spectrum of electromagnetic waves is the narrow colored band. Source: F. Zapata.

Natural light energy

The natural source of light energy par excellence is the Sun. Being a star, the Sun has at its center a nuclear reactor that transforms hydrogen into helium through reactions that produce immense amounts of energy.

This energy leaves the Sun in the form of light, heat and other types of radiation, continuously emitting about 62,600 kilowatts for each square meter of surface -1 kilowatt is equivalent to 1000 watts, which in turn is equal to 1000 joules / second-.

Plants use some of this large amount of energy to carry out photosynthesis, the important process that forms the basis of life on Earth. Another source of natural light, but with much less energy, is bioluminescence, a phenomenon in which living organisms produce light.

Lightning and fire are other sources of light energy in nature, the former are not controllable and the latter has accompanied humanity since prehistoric times.

Artificial light energy

As for artificial sources of light energy, they require converting other types of energy, such as electrical, chemical or calorific, into light. Incandescent bulbs fall into this category, whose extremely hot filament emits light. Or also the light that is obtained through combustion processes, like the flame of a candle.

A very interesting source of light energy is the laser. It has many applications in various fields including medicine, communications, security, computing, and aerospace technology, among others.

Figure 3. A cutting machine uses a laser to make high-precision industrial cuts. Source: Pixabay.

Uses of light energy

Light energy helps us communicate with the world around us, acting as a carrier and transmitter of data and informing us of environmental conditions. The ancient Greeks already used mirrors to send signals in a rudimentary way over long distances.

When we watch television, for example, the data it emits, in the form of images, reaches our brain through the sense of sight, which requires light energy to leave an imprint on the optic nerve.

By the way, for telephone communication, light energy is also important, through so-called optical fibers that conduct light energy, minimizing losses.

All we know about distant objects is information received through the light they emit, analyzed with various instruments: telescopes, spectrographs, and interferometers.

The former help to collect the shape of objects, their brightness - if many photons reach our eyes it is a shiny object - and their color, which depends on the wavelength.

It also gives an idea of ​​its movement, because the energy of the photons that an observer detects is different when the source that emits it is in motion. This is called the Doppler effect.

Spectrographs collect the way this light is distributed - the spectrum - and analyze it to get an idea of ​​the composition of the object. And with an interferometer, you can distinguish light from two sources, even if the telescope does not have enough resolution to distinguish between the two.

The photovoltaic effect

The light energy emitted by the Sun can be converted into electricity thanks to the photovoltaic effect, discovered in 1839 by the French scientist Alexandre Becquerel (1820-1891), father of Henri Becquerel, who discovered radioactivity.

This is based on the fact that light is capable of producing an electric current, by illuminating semiconductor silicon compounds that contain impurities of other elements. It happens that when the light illuminates the material, it transfers energy that increases the mobility of the valence electrons, and thus increases its electrical conduction.

Obtaining

Since its inception, humanity has sought to control all forms of energy, including light energy. Despite the fact that the Sun provides an almost inexhaustible source in the daytime hours, it was always necessary to produce light in some way to protect itself from predators and continue performing the tasks begun during the day.

It is possible to obtain light energy through some processes that are controllable in some way:

-Combustion, when burning a substance, it oxidizes, giving off heat and often light during the process.

-Incandescence, when heating a tungsten filament for example, like those of electric bulbs.

Figure 4. Incandescent bulbs work by passing an electric current through a tungsten filament. When heated, it emits heat and light. Source: Pixabay.

-Luminescence, in this effect light is produced by exciting certain substances in some way. Some insects and algae produce light, which is called bioluminescence.

-Electroluminescence, there are materials that emit light when they are stimulated by an electric current.

With any of these methods, light is obtained directly, which always has light energy. Now, producing light energy in large quantities is something else.

Advantage

-Light energy has an especially relevant role in the transmission of information.

-Using light energy from the Sun is free, it is also an almost inexhaustible source, as we have said.

-Light energy, by itself, is not polluting (but some processes to obtain it can be).

-In places where sunlight abounds throughout the year, it is possible to generate electricity with the photovoltaic effect and thus reduce dependence on fossil fuels.

-The facilities that make use of the light energy of the Sun are easy to maintain.

-Short exposure to sunlight is necessary for the human body to synthesize vitamin D, essential for healthy bones.

-Without light energy, plants cannot carry out photosynthesis, which is the basis of life on Earth.

Disadvantages

-It is not storable, unlike other types of energy. But photovoltaic cells can be backed by batteries to extend their use.

-In principle, the facilities that make use of light energy are expensive and also require space, although costs have decreased with time and improvements. New materials and flexible photovoltaic cells are currently being tested to optimize the use of space.

-The prolonged or direct exposure to sunlight causes damage to the skin and eyesight, but mainly because of ultraviolet radiation, which we cannot see.

Examples of light energy

Throughout the previous sections we have mentioned many examples of light energy: sunlight, candles, lasers. In particular, there are some very interesting examples of light energy, due to some of the effects mentioned above:

Led light

Figure 5. LED lights are more efficient than incandescent lights, as they give off less heat and emit light energy for longer. Source: Pixabay.

The name of LED light derives from the English Light Emitting Diode and is produced by passing a low intensity electrical current through a semiconductor material, which in response emits intense and high-performance light.

LED lamps last much longer than traditional incandescent bulbs and are much more efficient than traditional incandescent bulbs, in which almost all energy is transformed into heat, rather than light. That is why LED lights are less polluting, although their cost is higher than that of incandescent lights.

Bioluminescence

Many living beings are capable of converting chemical energy into light energy, through a biochemical reaction inside them. Insects, fish and bacteria, among others, are capable of producing their own light.

And they do it for different reasons: protection, attracting a mate, as a resource to catch prey, to communicate and obviously, to light the way.

References

1. Blair, B. The Basics of Light. Recovered from: blair.pha.jhu.edu
2. Solar energy. Photovoltaic effect. Recovered from: solar-energia.net.
3. Tillery, B. 2013. Integrate Science.6th. Edition. McGraw Hill.
4. Universe Today. What is Light Energy. Recovered from: universetoday.com.
5. Vedantu. Light Energy. Recovered from: vedantu.com.
6. Wikipedia. Light energy. Recovered from: es.wikipedia.org.