Maybe this is stating the obvious, but light gives humans the ability to see. When asked to describe what light is, however, not many people are able to come up with a scientific answer. From reflection and refraction to rainbows and prisms, we are exposed to the phenomenon of light every day.
The odds are good that light is the first thing you interact with each morning as rays from the sun stream through your window and help signal that it’s time to start the day. When we enjoy adequate exposure to natural light, our bodies rely on the earth’s cycles of lightness and darkness to identify when it’s time to go to sleep at night and when it’s time to wake up each morning.
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It’s easy to take light for granted, but it’s more complex than some may imagine. Here’s a brief primer on the light that passes through your bedroom window every day.
What Exactly Is Light?
Light is defined as a portion of the electromagnetic spectrum. It consists of various radio waves and gamma rays that interact with and travel through matter (such as atoms and molecules) to produce rays of light. The light then travels in waves or rays (a concept used to represent a line of light waves) at a speed that is nearly incomprehensible: approximately 299,792,458 meters (or 186,262 miles) per second.
When people refer to light, they are usually referring to only a very small portion of light that exists, which is known as “visible light.” Visible light includes beams or rays of light projected directly from the source responsible for creating the light. The sun, for instance, creates rays of light known as ultraviolet light. In turn, these rays become beams of light that are visible to the human eye as they reflect off the ozone and onto the surface of the Earth.
Light, or the lack of it, can play an important role in sleep. Darkness helps to cure our bodies and tell us that it’s time for bed. Helping to make your room a “sleep haven” by having blackout curtains, blocking noise with earplugs and ensuring your mattress is comfortable and relieves back pain, and you have a clean and supportive pillow will all help you fall asleep and stay asleep at night.
Because of the limitations of the human body, not all types of light are visible to the human eye. Although types of light such as radio waves, x-rays, and infrared light are not detectable by humans, they exist, invisible to the naked eye, all around the atmosphere.
Prisms From All Angles
A prism is generally a triangularly shaped object that is made out of glass or another clear material that is specifically designed with angles and polished, flat edges that are intended to refract light. Refracting light is simply the act of placing an obstacle in the way of light waves.
When an obstacle is placed in the way of light, it is forced to bend and change its path and speed. Through the use of a prism, light waves are slowed down enough that the human eye can detect the many colors that exist in visible light. This visible light is generally seen as white light, but as it is slowed down, the human eye can view the colors separately. It’s almost as if the white light fans out into its separate components.
The colors that can be seen through the use of a prism are often referred to as “ROY-G-BIV.” This is an acronym that makes it simple to remember the colors that appear in rainbows, which also appear when prisms are used. The colors that represent “Roy G. Biv” are red, orange, yellow, green, blue, indigo, and violet.
Rainbows Are Nature’s Magic Trick
A rainbow is very similar to the optical effect that is created through the use of a prism, except that it’s naturally occurring. For a rainbow to appear, certain conditions must be met in the atmosphere. Water droplets must exist in the sky as well as light from the sun. When the sunlight reflects off of the water particles in the sky, it is slowed down because light cannot travel as quickly through water as it can through empty space.
When the light waves are slowed down through refraction, the individual colors that make up visible light, usually seen as white light, can be seen reflected through the droplets of water. Again, it’s as if the white light fans out into its separate components, with the water droplet acting as the prism. The colors are continuous and appear in a bent arch as a result of light refraction.
Although most rainbows appear in the common shape of an arch, some rainbows may appear to be shaped in a full circle. The colors that are seen in rainbows are red, orange, yellow, green, blue, indigo and violet. Double rainbows can occur when the act of light refraction happens in multiple places at once.
Although they are a beautiful natural occurrence that has often been thought of as mystical, rainbows are simply an optical illusion that is created by naturally occurring water particles and sunlight in the atmosphere.
Additional Resources on Light:
- The Science of Light
- The Basics of Light
- What is Light and How Does it Travel?
- Newton’s Particle Theory of Light (PDF)
- Refraction of Light
- Types of Light
- Lights, Prisms and the Rainbow Connection
- Optics of Prisms
- Reflection, Refraction and the Prism (PDF)
- Bending Light Experiment
- Light and Dispersion
- About Rainbows
- Recipe for Rainbows
- Rainbows and Other Optical Effects
- Light and Color
- Lights, Lasers, and Illusions