Visible Light's Journey Through Various Mediums

Visible light is a form of electromagnetic radiation, which is transmitted in waves or particles at different wavelengths and frequencies. It is the only portion of the electromagnetic spectrum that can be detected by the human eye. As light travels through space, its frequency slowly diminishes and we observe this as a redshift, where light drops towards the red end of the spectrum. Light can pass through some objects, such as a pane of glass or clear plastic, and obstacles that allow light to pass through unimpeded are called transparent.

Through a prism

Light is a form of electromagnetic radiation, which is transmitted in waves or particles at different wavelengths and frequencies. This broad range of wavelengths is known as the electromagnetic spectrum.

Visible light is the portion of the electromagnetic spectrum that can be detected by the human eye. Our eyes contain specialized cells, called cones, that act as receivers tuned to the wavelengths of this narrow band of the EM spectrum.

A prism is a piece of glass or plastic in the shape of a triangle. When the full spectrum of visible light travels through a prism, the wavelengths separate into the colors of the rainbow because each color is a different wavelength. This is because the different colors of light travel at different speeds inside the glass. Violet has the shortest wavelength, at around 380 nanometers, and red has the longest wavelength, at around 700 nanometers. Violet travels the slowest so it is on the bottom and red travels the fastest so it is on the top.

As the light passes through the prism, it bends at different angles depending on the wavelength of the color. This is because what is called the index of refraction, or the ratio of the speed of light in a vacuum to the speed of light in a material, is increased for the slower-moving waves (i.e. violet). The higher index of refraction means that violet light is bent the most, and red is bent the least because of its lower index of refraction, and the other colors fall somewhere in between.

Through water

Light travels fastest in a vacuum and moves slightly slower in materials like water and glass. When light passes through water, it slows down. The depth of the water will determine the colours of light that are noticeable underwater.

Visible light is a combination of many colours. Each colour is a different wavelength. Violet has the shortest wavelength, at around 380-400 nanometres, and red has the longest wavelength, at around 650-700 nanometres. When light passes through water, the longer wavelengths like red are absorbed more quickly than the shorter wavelengths like blue. This is why red fish appear nearly black at 20 metres. At 40 metres, saltwater has absorbed nearly all the red visible light, yet blue light is still able to penetrate beyond these depths.

The intensity of light also decreases as it travels through water. Within the first 10 metres, water absorbs more than 50% of visible light energy. Even in clear tropical water, only about 1% of visible light—mostly in the blue range—penetrates to 100 metres.

The sun is the dominant source of visible light waves that our eyes receive. The outer-most layer of the sun's atmosphere, the corona, can be seen in visible light. However, it is so faint that it can only be seen during a total solar eclipse because the bright photosphere overwhelms it.

Through glass

Visible light can travel through glass. Light travels at a speed of 299,792 kilometres per second (about 186,282 miles per second) and moves slightly slower in materials like water or glass.

Glass is a solid, but it is transparent, meaning that light passes through it. When something is clear, like glass, visible light passes straight through it without being absorbed or reflected. This is because the electrons in a glass molecule are not at the right energy level to absorb visible light.

However, clear glass does absorb other wavelengths of light, such as ultraviolet and infrared or heat. Glass can be coloured by adding light-absorbing substances, such as copper or chromium. Because some visible wavelengths pass through coloured glass, we can still see through it.

When light passes through a dense glass prism, different colours of light bend by slightly different amounts. Blue light, for example, bends slightly more than red light. This is why a prism breaks white light up into a rainbow of different colours.

Through a vacuum

Light travels fastest in a vacuum at a speed of 299,792 kilometres per second (approximately 186,282 miles per second). This is also known as the speed of light, and it is the universe's fastest possible speed. Light travels in straight lines in all directions from its source when there are no obstacles in its path.

Light travels through the vacuum of space. It can cover the distance from the Sun to the Earth in 8 minutes and 17 seconds. The speed of light is so fast that during a storm, you will always see lightning before hearing thunder.

As light travels through space, its frequency slowly diminishes, and its wavelength increases. This phenomenon is called a redshift. The farther the light travels, the more its frequency diminishes and its wavelength increases. This causes the light to shift toward the red end of the spectrum.

The speed of light is calculated by multiplying the wavelength by the frequency. Light waves have wavelengths between 400 and 700 nanometers. Red light has longer waves of around 700 nm, while blue and purple light have shorter waves of around 400 nm.

Through space

Light travels at a speed of about 299,792 kilometres per second (approximately 186,282 miles per second) through a vacuum. In fact, light travels fastest in a vacuum and moves slightly slower in materials like water or glass. This is the speed at which light traverses space.

Light is a form of electromagnetic (EM) radiation, which is transmitted in waves or particles at different wavelengths and frequencies. This broad range of wavelengths is known as the electromagnetic spectrum.

Visible light is the portion of the electromagnetic spectrum that can be detected by the human eye. It is a type of electromagnetic radiation, as are radio waves, infrared radiation, ultraviolet radiation, X-rays, and microwaves.

As light travels through space, its frequency slowly diminishes, and we observe this phenomenon as a redshift, the tendency of visible light to shift toward the red end of the spectrum. The farther the light travels, the greater the degree to which its frequency diminishes as its wavelength increases.

The electromagnetic spectrum, from highest to lowest frequency wavelengths, is as follows:

• Radio waves
• Microwaves
• Infrared (IR)
• Visible light
• Ultraviolet (UV)
• X-rays
• Gamma rays

Visible light, which sits roughly in the middle of the spectrum, has wavelengths between 380 and 700 nanometers. Violet has the shortest wavelength, at around 380 nanometers, and red has the longest wavelength, at around 700 nanometers.

The Sun is the dominant source of visible-light waves that our eyes receive.

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