Visible Light: Sun-Bound Travel Explained

Visible light is a form of electromagnetic radiation, which includes radio waves, infrared radiation, ultraviolet radiation, X-rays, and microwaves. The human eye can only detect a small portion of this radiation, which we call visible light. The visible light spectrum ranges from 380 to 740 nanometers, with violet possessing the shortest wavelength and red possessing the longest. The Sun is the dominant source of visible light waves that our eyes receive. Light from the Sun travels in parallel beams towards Earth, with the Sun emitting light in pretty much every direction at random. However, as the Sun is so far away from Earth, most of the photons emitted do not reach us. Only those photons that are heading towards the Earth actually get there, and they travel in more or less parallel directions.

The sun's light travels in parallel beams towards the Earth

The Sun is the dominant source of visible light waves that our eyes receive. The light travels in a range of wavelengths, including ultraviolet and infrared radiation, but we can only see the visible light.

The Sun's light appears to travel in parallel beams towards the Earth. However, close to the Sun's surface, the light is emitted in random directions. The Sun is far away from the Earth, so most of the photons emitted do not reach us. Only the photons that are heading towards the Earth get there, and they are travelling in more or less the same direction.

The Earth is small and far away from the Sun, so the photons that reach us are almost parallel. This is why we can see sunbeams as distinct lines. Sunlight forms a light beam (a sunbeam) when it is filtered through clouds, leaves, or windows.

The human eye can detect wavelengths from 380 to 700 nanometres. Our eyes contain specialised cells, called cones, that act as receivers tuned to the wavelengths of this narrow band of the electromagnetic spectrum.

The sun's light is a form of electromagnetic radiation

The energy released in the sun's core then makes its way to the outer regions of the sun and is radiated or emitted away in the form of electromagnetic radiation. A particle of electromagnetic radiation is known as a photon. Photons can only travel a few millimeters before they hit another particle in the sun, are absorbed, and then released again. It can take a photon as long as 50 million years to travel all the way through the sun's radiative zone.

The sun's light falls within the portion of the electromagnetic spectrum that can be detected by the human eye. This range of wavelengths is called visible light. Typically, the human eye can detect wavelengths from 380 to 700 nanometers or 0.4 to 0.7 micrometers. Visible light is all the light we can see with our eyes. We cannot see ultraviolet or infrared radiation, but their effects can still be detected. For example, a sunburn is caused by ultraviolet radiation.

The sun's light is not just limited to visible light, however. The sun emits radiation at all wavelengths, and approximately 44% falls within visible-light wavelengths. About 40% of the sun's radiation is at wavelengths of infrared or longer, and 10% is at wavelengths of ultraviolet or shorter.

The sun's light travels through the Earth's atmosphere

The Sun is the dominant source of visible light waves that reach the human eye. The Earth's atmosphere allows for the transmission of visible light, which is a form of electromagnetic radiation.

Visible light travels through the Earth's atmosphere via the optical window region of the electromagnetic spectrum. The ozone layer absorbs almost all UV light, but this does not affect the transmission of cosmic light, such as sunlight.

The Sun's light travels in parallel beams towards the Earth. This is because, although the Sun emits photons in all directions, the Earth is far away enough that only those photons travelling towards the Earth are visible from the planet.

The part of the Sun that emits sunlight is called the photosphere. This is the visible surface of the Sun and is also one of its coolest layers, at around 6700°C. The light energy from the photosphere travels through space, and some of it reaches the Earth.

Above the photosphere are the chromosphere and the corona, which is the Sun's outermost layer and atmosphere. The corona is much hotter than the photosphere, reaching temperatures of 2-5 million°C. During a total solar eclipse, the corona can be seen shining out into space.

The sun's light is visible to the human eye

The sun is a powerful source of light and energy, and its light is visible to the human eye. The sun emits light through a process called fusion, which occurs when two atoms are heated and compressed, causing their nuclei to merge and form a new element. This process results in the creation of photons, which are particles of light. These photons undergo a long journey before they reach us on Earth.

The light we see from the sun is a result of nuclear fusion happening in its core. The sun's immense size, with a radius of 696,000 km, allows it to contain a vast number of atoms undergoing fusion. This process generates an enormous amount of energy, with 650 million tons of hydrogen fused into helium every second. The heat energy produced by this constant fusion keeps the sun's core at an extremely high temperature of 15,000,000 degrees Kelvin.

The photons created in the sun's core take about 40,000 years to reach its surface, travelling in a zigzag path from atom to atom. Once they reach the surface, they stream out into space, illuminating the Earth and our solar system. The journey of these photons from the sun's core to its surface and then to Earth provides us with a glimpse into the sun's past.

The light from the sun that reaches Earth is in the form of electromagnetic waves, with visible light being the most intense. The human eye has evolved to adapt to the sun's spectrum, allowing us to perceive sunlight as yellow. This perception is due to the sun's surface temperature of 6,000 degrees Kelvin, which corresponds to the wavelength of light our eyes are most sensitive to, around 500 nanometers. This sensitivity enables us to distinguish colours and perceive sunlight as yellow.

The sun's light takes approximately 8 and 1/3 minutes to reach us, travelling at an incredible speed of 186,000 miles per second or 300,000 kilometres per second. This means that when we look at the sun, we see it as it was 8 minutes ago. The sun's brightness, size, and proximity to Earth make its light visible to the human eye, providing us with the energy and illumination necessary for life on our planet.

The sun's light is essential for life on Earth

The Sun is a yellow dwarf star, a hot glowing ball of hydrogen and helium, and is the largest object in our solar system. It is the only star in our solar system and is the source of almost all the energy on Earth. The Sun's gravity holds the solar system together, keeping everything from the biggest planets to the smallest bits of debris in orbit around it.

The Sun's light appears to travel in parallel beams towards the Earth. This is because, although the Sun emits photons in all directions, the Earth is far away, so only those photons heading towards the Earth reach it, and these photons are all travelling in roughly the same direction.

The Sun's light travels through space, and some of it reaches the Earth. This light travels in a range of wavelengths, including visible light, ultraviolet, and infrared radiation.

Visible light is the segment of the electromagnetic spectrum that the human eye can view. The human eye can typically detect wavelengths from 380 to 700 nanometers. All electromagnetic radiation is light, but we can only see a small portion of this radiation—the portion we call visible light.

The Sun's light also allows us to see. The human eye contains specialised cells, called cones, that act as receivers tuned to the wavelengths of this narrow band of the electromagnetic spectrum.

The Sun's light also has a range of other uses and benefits. For example, laser altimetry is an example of active remote sensing using visible light. NASA's Geoscience Laser Altimeter System (GLAS) instrument uses lasers and ancillary data to calculate the elevation of Earth's polar ice sheets. Changes in elevation over time help to estimate variations in the amount of water stored as ice on our planet.

The Sun's light is also important for astronomy. The close examination of the visible-light spectrum from the Sun and other stars reveals a pattern of dark lines—called absorption lines. These patterns can provide important scientific clues that reveal hidden properties of objects throughout the universe. Certain elements in the Sun's atmosphere absorb certain colours of light. These patterns of lines within spectra act like fingerprints for atoms and molecules.

Frequently asked questions