Solar Radiation


Temperatures so high occur inside the Sun that they generate nuclear-type reactions and that in turn create energy. This energy is released in the form of solar radiation. Radiation emissions have varying degrees of intensity. Not all this radiation reaches planet Earth, as some waves (the most damaging) are filtered or absorbed by atmospheric gases, especially ozone. The solar radiation that reaches the earth’s surface is essential for living beings. Processes such as photosynthesis, winds and global warming depend on it. Directly or indirectly, solar radiation is used by humans to obtain energy.


What is solar radiation?

The Sun emits electromagnetic radiation known as solar radiation. Electromagnetic waves arise from thermonuclear reactions that occur inside the star king. There temperatures reach up to 20 million degrees. The solar radiation that is released leaves in different directions without the need for a physical vehicle to propagate it and reaches the Earth. However, not all waves touch the earth’s surface, as some are trapped by the atmosphere along the way.


Characteristics of solar radiation

  • It is a consequence of nuclear mergers within the Sun.
  • Its distribution is broad spectrum , that is, it does not clump together at a specific frequency.
  • Satellite measurements indicate that the amount of energy received by solar radiation outside the atmosphere is approximately 1366 Wm-2
  • The energy leaves the source (Sun) and diffuses directly without the need for other matter.
  • Its visible spectral components (light) are located in “bands of photosynthetically active radiation” (PAR). Its concentration ranges from 400 to 700 micrometers (nm). This represents 41% of the total radiation.

Radiation subbands

In PAR, radiation sub-bands are generated and classified by color:

  • Blue-Violet (400 to 490 nm)
  • Green (490 to 560 nm)
  • Yellow (560 to 590 nm)
  • Red- Orange (590 to 700 nm)

Invisible radiation

There are radiation that is not observable because its ” wavelength ” is absorbed mostly by oxygen and ozone in the atmosphere. However, its effects are very harmful. These are ultraviolet and infrared radiation. The first causes serious damage to human health and the second to the energy emitted by the Earth and absorbed by the so-called “ greenhouse effect ”.

Types of ultraviolet radiation

This radiation comes in UV-A, UV-B and UV-C types. Their “wavelengths” are between 150 nm and 400 nm. A large part of these rays do not reach the Earth and of those that do reach 99% belongs to type A, which is the least harmful to humans. Type B passes, but very little and C does not pass through the ozone layer and atmospheric oxygen. UV_B radiation is the one that is considered the most serious for health, as there are studies that link it with the appearance of skin cancer.

Types of solar radiation

Science classifies solar radiation into four types , according to how it is received by objects located on the surface of the Earth:

  • Diffuse radiation: when radiation passes through the atmosphere and is reflected or absorbed by clouds. Dust, mountains, buildings, the ground, etc. also influence. This makes your trajectory go everywhere. No shadows are generated on interfered with objects.
  • Direct radiation: it leaves the Sun and does not change its direction when it reaches the surface. Create precise shadows on intercepted objects.
  • Reflected radiation: is the radiation that is reflected by the terrestrial plane. The amount of radiation depends on the Albedo (“surface reflection coefficient”). Vertical planes will receive more radiation and horizontal planes none.
  • Global radiation: sum of the three previous radiation.

How is solar radiation measured?

To measure solar radiation, a sensor called a Pyranometer is required. There are two types, thermal and photovoltaic. Measurement is carried out by placing the device on a horizontal surface without shadows and facing south. The tool will quantify the density of the radiation flux in kW / m² in an area of ​​180 degrees.


All living things take advantage of solar energy for their benefit and vital functions. Without solar radiation, plants would not carry out the photosynthesis process . The animals that feed on plants and those that feed on these, make use of the energy provided by the sun king. Humans also use solar energy by using fossil fuel (which preserves it from its formation millions of years ago) or from hydroelectric power through condensed water at the top and that later went through the evaporation process. New forms of exploitation such as wind energy that works with the wind that forms with the warming of the Earth’s surface is another example.

More uses of solar radiation

As part of an ecological campaign that various organizations, foundations and governments have undertaken, more and more alternatives for the use of clean energy are being created. This is what comes naturally, like solar radiation. Through panels that absorb this radiation and energy, many homes and buildings use them to generate electricity. This practice, although still expensive to install, is gaining more and more followers. On the other hand, devices that work or are charged with the sun’s rays such as watches, calculators, among others, have already become popular.

Factors that affect the levels of Solar Radiation

Our planet receives approximately 1 366 W / m² from the king star. This is related to the atmosphere and the perpendicularity of the plane with the rays that enter. This decreases its passage by up to 75%, in addition the atmosphere also filters the arrival. Reflection, gases and clouds also play a role. When passing through the atmosphere, half of the radiation that enters is not altered and 50% of it contributes to the evaporation of water bodies. Ultraviolet rays, so harmful to health, are absorbed by the ozone layer. Environmental pollution, which weakens this layer and alters the atmosphere, reduces its effectiveness and raises radiation levels.

How solar radiation affects the atmosphere

Solar radiation does not heat the atmosphere directly , but it does so through reflection. That is, with the rays that pass through it and bounce off the ground, oceans and seas. With the industrialization of cities and consequently the emission of gases that pollute and alter the atmosphere. Natural filters do not work effectively. In addition, holes have been created (especially in the ozone layer) that make the passage of solar radiation greater and the planet suffer. Drier areas have been created, ecosystems disrupted and animal species extinct.

Health consequences

The increasing passage of ultraviolet radiation due to the weakening of the ozone layer is perhaps the most worrying factor for humans. These are very harmful to health, especially for the skin, as it interferes with DNA molecules. It has been proven that its continuous and excessive exposure can lead to cancer, a disease that reduces life expectancy. Likewise, it causes premature aging of the skin, dry skin and burns. For this reason, it is advisable to use sunscreen to avoid getting sick, even if there are clouds. Only those of the cumulus class decrease radiation. The rest do not act as a filter, on the contrary, some produce the “magnifying glass effect”.

positive effects

Solar radiation, in a moderate way, provides health benefits when not exposed to excess. It works as a natural synthesizer of vitamin D, which contributes to the good condition and development of the bone system. Also, there are studies that indicate that it works as an antidepressant, as it influences mood. When the season has fewer hours of sunshine, the so-called “Seasonal Affective Disorder” may appear, which positively yields by increasing the hours of sunshine per day. Likewise, in a moderate way, receive the sun’s rays for skin conditions such as acne, atopic eczema and psoriasis. The important thing is not to abuse radiation to enjoy its benefits.

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